Why is 87 Octane gas $2.34 but Diesel is $3.65?

[jinjuku]

I know my Jetta has a passive DPF (no fluid required) and driving at highway speeds is enough for it to burn off particulate. Been reading about how some shops misdiagnose and replace the turbo only to then have the same problem and UNCLOG (not replace) the DPF filter. Meaning the turbo was most likely fine.

Yikes.

Good information to have. Here is a good explanation that just helped me wrap my brain around it:

Passive or active DPF regeneration symptoms and conditions (linked for attribution).
The passive regeneration occurs with no action taken by the car's computer. It occurs with higher sustained engine loads like freeway driving or fast acceleration onto the highway when exhaust gasses are hotter. These types of loads will produce exhaust gas temperatures (EGT) of about 350-500oC which thoroughly heat up and burn the DPF. If the car has only short stop-go trips, the exhaust doesn't have a chance to have a good passive burn off and will have more active regens or clog.

The active regeneration "self clean" occurs when filter soot loading is beyond 45% or every 466-621 miles (750-1000 kilometers), whichever is sooner. EGR is shut off and the fuel injectors squirt a little fuel into the engine cylinders after combustion (post combustion injection) that travels to the oxidation catalytic converter and oxidizes to raise EGT to around 600-650oC. The gasses travel to the DPF and burn up the trapped particulates.

During an active regen the car's computer also temporarily increases turbo boost about 2-4 psi to make up for any lost power. Engine rpm also goes up around 200 rpm on the 2.0L engine. A cycle lasts about 10 minutes and if you shut the engine off in the middle of an active regen cycle, you'll hear the radiator fans in the front of the car running fast (even after the car is shut off) and you may smell a burning rubber type odor. It will resume once you exceed 38 mph after the next engine start (and the exhaust is warm enough).

If the car still can't do an active regen and soot loading reaches 50-55%, it will try to force a 15 minute regen cycle. If you interrupt it by shutting the engine off, the active regen cycle won't finish. There is normally no light or indicator to show when the car is doing an active DPF cycle. If the cycle was interrupted by engine shut off, it'll try again before lighting the DPF warning light on the dashboard (pictured right). If that happens, drive at about 40 mph for at least 10 minutes in 4th or 5th gear at 2000RPM (Disclaimer: faster would be fine as long as you don't exceed the speed limit).

At 75% loading, the glow plug light will also come on. If you see the warning, go to have the car service or go to the dealer so they can explain the warning lights to you. It's still possible to do a service regeneration, a manually started active DPF regen.

In the 2.0L engine, the automatic active regen is blocked by the car's computer once DPF loading reaches 40 grams. The service regen must be manually initiated using the procedure below. I'm not sure if the service regen is the same as the emergency 95% regen so try both methods below.

If clogging reaches 95% (45 grams) it must be manually removed and cleaned since all that combustion could damage or melt the filter due to extreme heat and pose a fire risk. There's a chance the repair would not be covered by the car warranty (maybe the federal emissions warranty) if you ignored the warning light or if the clogging is caused by your driving style.

 

[Gordonj]

Well,well, well, I guess I should stop listening to the truck and tractor sales guys and now investigate this a bunch further.....

At least it is a nice truck....

Thanks for filling the gaps Doc and everyone.

 

[TLS Guy]

I couldn't agree more Doc.
My brother has an F450 work truck (1yr old) the DPF clogged and blew the turbo off the truck.
The average person doesn't know how many half baked and dangerous laws come out of the EPA.
DEF causes very serious de-oxidation of water bodies and damage of the aquatic.
Reminds me of how bad the EPA's forced use of MTBE was.

Rich what is your source for aquatic damage to water bodies?

Urea is not toxic. In cases were urinary bowel fistulas occur, the blood urea can get really high, but patients are alert. What gets them into trouble is hperchloremic acidosis. They are not harmed by the urea.

In the hot exhaust gas urea in broken down to Ammonia. When combined with the catalyst, plus carbon monoxide and nitrous oxide you get nitrogen and water.

This is the formula for urea.

This is the total process: -

DEF (Diesel Engine Fluid) is a 32.5% solution of Urea (NH2)2CO. When the urea solution is injected into the hot exhaust gas stream the water evaporates. The urea thermally decomposes to form ammonia and isocyanic acid:

(NH2)2CO → NH3 + HNCO
The Isocyanic acid hydrolyses to carbon dioxide and ammonia:

HNCO + H2O → CO2 + NH3
The overall reduction of NOx by urea is:

2(NH2)2CO + 4NO + O2 → 4N2 + 4H20 + 2CO2
So the four molecules of Nitrous oxide, and a molecule of carbon monoxide, and up giving you 4 molecules of nitrogen, four molecules of water and two molecules of carbon dioxide. I don't see anything toxic in this.

The real problem is the DPF filter.

There is abundant evidence that these small carbon particles are very damaging to health and increase cardiovascular mortality. In addition they are the principal cause of non cigarette related lung cancer.

Studies of cardiovascular mortality have been conducted around the world. Along urban interstates CV mortality is increased seven to 8 fold, and you have to get at least 7 miles from the interstate to get back to baseline.

So removing them is important, the problem is that many of the removal methods can have a devastating effect on engines, especially in very cold temperatures, where regeneration is often incomplete.

The regs came out of the EU (EUSSR) Tier 1 though four. We are now past Tier 4 and the regs have to be enforced here because of trade agreements.

Banning of diesel engines from London is now under consideration and two burroughs already have. France just announced it will at least consider a total diesel engine ban.

 

[Rickster71]

I saw this initially: In the UK, the storage of DEF is now under scrutiny of the Environment Agency who are proposing new controls following a number of spills of DEF into the environment. Although not toxic, DEF can cause the catastrophic de-oxidation of water bodies leading to damage of the aquatic environment.

(That led me to the link below):
http://www.oiltanksupplies.co.uk/blue-stream/

1. Urea solution is very polluting to surface water and groundwater.
2. It has caused several serious pollution incidents from spills at farms where it was stores and used as a fluid fertiliser.
3. Urea solution contains ammonia and is corrosive to some metals, such as copper and its alloys.
4. If tanks and pipework become corroded there is a higher risk of a spill that could cause pollution – which is against the law and could lead to a fine.

It’s important that ERS are stored in containers that are specifically designed and manufactured from materials that are suitable for the use with urea. This also applies to all storage ancillary equipment, such as valves, dispensing nozzles and pipework. Urea based ERS are soluble in water and should be kept out of surface water drainage systems discharging to the environment.

They will not be removed in an oil separator so it’s important to isolate drainage from your dispensing area from the surface water system to reduce the possibility of spills and drips causing pollution.

In the UK, the storage of Diesel Exhaust Fluid (DEF known as Adblue in Europe) is now under scrutiny of the Environment Agency who are proposing new controls following a number of spills of DEF into the environment. Although not toxic, DEF can cause the catastrophic de-oxidation of water bodies leading to damage of the aquatic environment.


My$0.02
I do understand that the EPA and the Keystone Cops both have the best of intentions.
However their methods often end with dubious results.
Damage from Ethanol
Damage from MTBE
IMHO we are trying to put a band-aid on the real problem, that is Over Population.

 

[Sheep]

Actually, diesel engines do not inherently last longer. That's folklore. The reason some diesel engines last longer is that they're built more robustly and are therefore more expensive than typical gasoline engines. If you built a gasoline engine to the same standard it would last longer. For example, the slow-turning Ford 4.6L OHC V8 so loved by the taxi and towncar industry is well known for going 300K miles in city traffic without a rebuild. Combine that with an air suspension (no shocks needed) and you have a car with a big back seat that needs very little mechanical maintenance. (And I've noticed most often gets very little maintenance...)

Diesel engines do have one very distinct advantage for trucks. Compression ignition is very friendly to forced induction. Just add some weight, cost, and complexity and you get massively increased horsepower without negative side effects like you do with gasoline engines. Since trucks are less sensitive to diesel NVH challenges, weight and size aren't critical factors (so you can use iron blocks and heads and you have room for routing turbo plumbing), and low rpm torque is critical, a turbo diesel is a match made in... well, Detroit. On the other hand they pollute more and diesel owners who refuel themselves may smell a little funny.

Actually, those Crown Vic last so long not because they are better built, but because they don't heat cycle as often. They leave them running all the time, they almost never cool down. THAT is what kills an engine (of sufficient build and design).

SheepStar

 

[Irvrobinson]

Actually, those Crown Vic last so long not because they are better built, but because they don't heat cycle as often. They leave them running all the time, they almost never cool down. THAT is what kills an engine (of sufficient build and design).

SheepStar

You really don't know what you're talking about, do you?

 

[Sheep]

You really don't know what you're talking about, do you?

Sure I do. Heat expansion and contraction are the cause of major wear combined with cold operation (start up) in an ICE. There is Taxi's here in Vancouver with nearly a million kilometers on the same engine. You can prepare a statement if you want while I consult with the technicians at any of the 13 dealers in my auto group in the lower mainland if you want? Or you can keep your snide remarks, I'm prepared for either.

SheepStar

 

[jinjuku]

I've always wondered what a reasonably built engine that was on most the time would do vs one that is constantly cycled on/off.

The Crown Vic's and Lincoln Continentals that are used for taxi service always have very high mileage and and I wonder how that would compare with the average life span (in mileage) with a typical consumer driven Vicky or Continental.

 

[Irvrobinson]

Yeah, you go do your consulting with the techs. Idling is just great for gasoline engines, as is stop and go driving. You might want to think about low-rpm design targets, iron engine blocks, conservative compression ratios, chain-driven cams, properly engineered valve guides, and properly engineered cooling systems and coolant passages within the engine.

 

[Irvrobinson]

I've always wondered what a reasonably built engine that was on most the time would do vs one that is constantly cycled on/off.

The Crown Vic's and Lincoln Continentals that are used for taxi service always have very high mileage and and I wonder how that would compare with the average life span (in mileage) with a typical consumer driven Vicky or Continental.

Taxis are cycled on and off quite a bit during idle periods. When I see them lined up at the airports or hotels they usually have their engines turned off, to save gas. Diesels idle efficiently, gasoline engines don't.

In the case of Crown Vics the most popular option is to get decommissioned police cars for use as taxis. The "police interceptor" models have numerous different parts, all of which contribute to longevity rather than performance. It was actually Lincoln Town Cars I was speaking of in the 300K mile rebuild range, which are all built using the standard consumer design.

 

[Sheep]

Taxis are cycled on and off quite a bit during idle periods. When I see them lined up at the airports or hotels they usually have their engines turned off, to save gas. Diesels idle efficiently, gasoline engines don't.

In the case of Crown Vics the most popular option is to get decommissioned police cars for use as taxis. The "police interceptor" models have numerous different parts, all of which contribute to longevity rather than performance. It was actually Lincoln Town Cars I was speaking of in the 300K mile rebuild range, which are all built using the standard consumer design.

I think you confusing "turning it on and off" and "cooling it down and heating it back up". You can turn a car on and off lots, but it's still warm for quite a while afterwards.

SheepStar

 

[jinjuku]

Taxis are cycled on and off quite a bit during idle periods.

I think turned off and on is different then completely cooling and then heating.

 

[Sheep]

I've always wondered what a reasonably built engine that was on most the time would do vs one that is constantly cycled on/off.

The Crown Vic's and Lincoln Continentals that are used for taxi service always have very high mileage and and I wonder how that would compare with the average life span (in mileage) with a typical consumer driven Vicky or Continental.

I think those comparisons are already known. I deal with shops that service fleet vehicles and besides maintenance parts they don't have as many long life costs. Look at your car now, how old is it, how many miles/kilometers, and what has gone wrong (that isn't something like bluetooth)? You see bushings, struts, stuff like that. Then you reach that point when oil starts coming out the pipe, and leaking around the engine. Rubber seals harden up after all the heat cycling. It's totally normal to have this happen, it's part of owning a car.

SheepStar

 

[jinjuku]

I think those comparisons are already known.

They may be well known to some people. I wouldn't be in that group ;-)

 

[Irvrobinson]

I think you confusing "turning it on and off" and "cooling it down and heating it back up". You can turn a car on and off lots, but it's still warm for quite a while afterwards.

SheepStar

I'm not confusing anything, Sheep. Turn a car off for 20 minutes and it cools. Not cold, but it cools. Of course, in the first few minutes after an engine is turned off there's usually heat soak as the engine stays hot for a short period while the cooling system isn't running, but we probably shouldn't go there, as that's none too good for gasoline engines either. Regardless, that's not my point. My point is that saying that keeping an engine hot is the primary determinant in how long it'll last is silly. You might have gotten away with highway miles make an engine last longer, because I think there's at least good anecdotal evidence it's true, but that's not how taxis are used. Stop and go driving and idling are high-wear use conditions for gasoline engines.

 

[Sheep]

I'm not confusing anything, Sheep. Turn a car off for 20 minutes and it cools. Not cold, but it cools. Of course, in the first few minutes there's usually heat soak as the engine stays hot for a short period while the cooling system isn't running, but we probably shouldn't go there either, as that's none too good for gasoline engines either. Regardless, that's not my point. My point is that saying that keeping an engine hot is the primary determinant in how long it'll last is silly. You might have gotten away with highway miles make an engine last longer, because I think there's at least good anecdotal evidence it's true, but that's not how taxis are used. Stop and go driving and idling are high-wear use conditions for gasoline engines.

The most wear intensive conditions for an engine is cold start up. Bar none. Stop and go is hard on a CAR. It's brakes, tires, suspension, but the engine is barely doing anything. Yes, low RPMs have a very high misfire %, but it's not as hard on the components. If you're driving like the gas and brake pedals are on off switches, yes you'll probably kill your engine early. But letting the engine idle is not going to blow the rings. With the move to DI becoming every manufactures new claim to fame, we're going to see carbon become the new big problem. Lexus is starting to go through it with the IS250, as it has only DI (IS350 has DI and Port Injection). I've seen intake valves with 40,000kms on them that looked worse then my 200+ thousand kilometer civic intake valves, they looked like exhausts valves.

SheepStar

 

[Irvrobinson]

The most wear intensive conditions for an engine is cold start up. Bar none. Stop and go is hard on a CAR. It's brakes, tires, suspension, but the engine is barely doing anything. Yes, low RPMs have a very high misfire %, but it's not as hard on the components. If you're driving like the gas and brake pedals are on off switches, yes you'll probably kill your engine early. But letting the engine idle is not going to blow the rings. With the move to DI becoming every manufactures new claim to fame, we're going to see carbon become the new big problem. Lexus is starting to go through it with the IS250, as it has only DI (IS350 has DI and Port Injection). I've seen intake valves with 40,000kms on them that looked worse then my 200+ thousand kilometer civic intake valves, they looked like exhausts valves.

SheepStar

Low RPMs do not have a high misfire percentage on modern cars. In fact, any misfires will trip your OBDII Check Engine Light.

 

[Sheep]

Low RPMs do not have a high misfire percentage on modern cars. In fact, any misfires will trip your OBDII Check Engine Light.

Yes they do. It's not a misfire percentage, it's the likeliness of a misfire (should have worded that better, my bad). I was driving around with one of the technicians at a Lexus dealership while he was monitoring the tech stream (laptop that hooks up to the OBD port). I was holding a gear and adjusting the RPMS and then letting it idle in neutral. You would see the % at 99 when it was idling, and when you revved it up it dropped down to very low levels.

SheepStar

 

[Irvrobinson]

Yes they do. It's not a misfire percentage, it's the likeliness of a misfire (should have worded that better, my bad). I was driving around with one of the technicians at a Lexus dealership while he was monitoring the tech stream (laptop that hooks up to the OBD port). I was holding a gear and adjusting the RPMS and then letting it idle in neutral. You would see the % at 99 when it was idling, and when you revved it up it dropped down to very low levels.

SheepStar

Percentage of what? I'll say it again, if an OBDII gasoline car misfires even once it throws a CEL. Go ask one of your buddy techs about that.

 

[Rickster71]

Too bad this thread went off the rails.
I was interested in TLS's thoughts on my reply post 24.