Is carbon buildup a myth nowadays?

[tpattgeek]

First of all, excuse my ignorance as I am more of an electrical guy than a mechanical guy, but I was just curious if anyone with modern day experience had some information they could share. Basically, my question is: People (usually people who like to go fast) sometimes say you should "get on" your vehicle to blow or burn off any carbon deposits. If that ever was true, would it still apply now? Would driving conservatively 100% of the time make a newer vehicle last longer? My vehicles (possibly irrelevant) are: 2007 Honda Civic, 1.8L R18A, daily commute and always brought to full operating temp, 40k miles and using M1 since 5k miles with 5k OCI (I know, it's overkill, but I don't care :)) 2010 Toyota Sienna, 3.5L 2GR-FE, family vehicle and always brought to operating temp, 4k miles currently and will have 4 free OC's with Toyota conventional oil, will probably use M1 starting at 20k miles and will stick with 5k OCI Another issue is, although I've been told conventional would be more than enough for my OCI's and driving habits, don't synthetics have more "detergents" or something that would be of more benefit even with 5k OCI? *** My goal *** To put as many miles as possible on these vehicles. The Civic will go to my stepson in ~8 years with ~100k miles. The Sienna will be the family vehicle for the next 20+ years.

 

[SERonBLAST]

There are direct injection engines that have this problem, Audi has the 2.0T that are pretty common for build up and with the DD being so slow and short, the temps just dont reach the level that will help stop it. And i would imagine that regular gas 87oct is a culprit as well.

 

[tpattgeek]

Not sure if you mean 87 for the Audi or 87 in general. I have put only Shell gas in both vehicles since the beginning of their life. Not trying to start a gas debate, but would 89 be best for my vehicles? I believe certain vehicles actually do run optimally on 87.

 

[Scotty1981]

My Civic gets better MPG and seems to run better on 87. I ran 89 for a while and MPG dropped I quickly went back to 87. MPG City Driving 87 Octane - 28/29 MPG 91 Octane - 24/25 MPG (I only ran this for 3 fill ups though)

 

[SERonBLAST]

Originally Posted By: tpattgeek

Not sure if you mean 87 for the Audi or 87 in general. I have put only Shell gas in both vehicles since the beginning of their life. Not trying to start a gas debate, but would 89 be best for my vehicles? I believe certain vehicles actually do run optimally on 87.

Yes, i was meaning for the Audi. I see the tail pipes on a lot of them just oozing out the black gunk. Other cars as well but Audi is my only study. I have used only Shells V-power 91 in all my cars since early last year when i heard about V-power. It is the only gas here with no ethanol in it. Before was only petro 91. See a trend? lol

 

[Kurtatron]

I believe carbon deposit problems are for older cars only. Carbon deposits form because of rich conditions. Today's cars are tuned to achieve as balanced a fuel mixture as possible. It is true however that when idling, a motor must run rich to maintain vibration free running. I read this somewhere, I wish I could find the link. So if you idle the car much, carbon buildup may be an issue. For the most part though, carbon buildup should not be an issue. My '92 Miata is notorious for carbon buildup. Pulling the sparkplugs reveals black crust coating on the pistons. The good news however is that the carbon actually helps my car maintain power. As the cylinders and valve guides wear, the motor loses compression. However, the carbon raises the compression ratio, boosting the power. My car actually uses carbon deposits as an advantage. I don't suggest you follow the age old adage, "rev the motor" to remove carbon. If you have a standard transmission, just don't run it very low revs. Avoid short shifting. Redlining the car incurs more wear and tear than carbon. How many dead cars have you heard of that died from carbon buildup vs. low compression and oil burning? Oil burning comes from either poor maintenance or hard driving lifestyle. IF you do get carbon problems, Techron is THE carbon removing stuff. Look it up. Really you shouldn't worry about carbon buildup.

 

[SERonBLAST]

I have used other gas in emergency but not ever lower than 91. Sunoco 94 is ok and adds a little bit more pep to my step in my Audi and SIR, but i just cant justify paying the price of 94. I see it as this, ethanol is at 10% and if ethanol is an octane booster than is that not false octane? I like the idea of not having ethanol.

 

[tpattgeek]

Originally Posted By: SERonBLAST

I have used other gas in emergency but not ever lower than 91. Sunoco 94 is ok and adds a little bit more pep to my step in my Audi and SIR, but i just cant justify paying the price of 94. I see it as this, ethanol is at 10% and if ethanol is an octane booster than is that not false octane? I like the idea of not having ethanol.

We don't have places like that around here. Not sure about other places in the USA, but we only have 87, 89, and 91, with MOST places stating it's up to 10% ethanol. My vehicles' manuals state that ethanol is OK (not that we'd have much of a choice). I used to put 91 V-Power in my 95 prelude because it called for 91. 87 seems to run just fine in these vehicles, and sorry if the carbon deposits are more related to gas than oil, but thanks for the info. you've all provided. Looks like my vehicles along with driving habits should help them run for a while with no issues :)

 

[Johnny]

On the oil question, most modern day conventional oils will handle your driving habits without a problem. But if using a synthetic at 5K helps you sleep better at night then stick with what you are doing. That's what I do and you don't have to answer to anyone else except yourself. And, there is no reason to wait until 20K to start using the Mobil 1 in your Sienna, unless you just like the free service from your dealer. I also pour a bottle of Gumout REGANE in the gas tank every 5K and I have never had a carbon deposit issue.

 

[Hokiefyd]

I do agree that carbon deposits are largely a thing of the past. However, there are still some things to consider. Most modern engines don't idle around like older engines used to (large V-8s that rarely spun faster than 2,000 RPM), but modern engines also use low-tension piston rings that can begin to stick when not exercised enough, promoting oil consumption. Cadillac's Northstar engine was a notable example of that. They designed the engine has a high performance engine, and if driven like one, they're fine. But driven as most Cadillacs are normally driven, to the country club and back at no more than 30 MPH, the rings would tend to stick up. With your two listed vehicles, tpattgeek, I wouldn't expect any issues. Both will likely be driven hard enough and fast enough to keep carbon deposits at bay. In addition, as someone else previously said, fuel control systems continue to advance, meaning fuel mixtures are kept under very tight control. As long as the piston rings stay in good shape, I wouldn't expect any issues.

 

[KrisZ]

I think we still have carbon deposits, may not be as severe, but carbon still builds up, just look at the exhaust pipes in your parking lot. Cars are made to run rich when cold to warm up cat. converters so cars that run a lot of short trips will have sooty exhaust tips. We also have other sources for carbon buildup, PCV and EGR, these also contribute especially during short trips. But because of knock sensors and fuel injection, carbon buildup usually will not affect performance until it is really severe, so that's why we may have the impression that there is no carbon build up.

 

[MariusVT]

Originally Posted By: Kurtatron

I believe carbon deposit problems are for older cars only. Carbon deposits form because of rich conditions. Today's cars are tuned to achieve as balanced a fuel mixture as possible.

I wouldn't say this is the case for all cars. I know mazda tuned their mazda6's in the 03-08 models to be extremely rich. I've seen plenty that hit a sub 10:1 AFR in the upper rpm range. It is also a suspected reason as why a the V6 cars have a problem with their precats getting clogged and blowing the motor.

 

[Jim Allen]

Originally Posted By: SERonBLAST

I have used other gas in emergency but not ever lower than 91. Sunoco 94 is ok and adds a little bit more pep to my step in my Audi and SIR, but i just cant justify paying the price of 94. I see it as this, ethanol is at 10% and if ethanol is an octane booster than is that not false octane? I like the idea of not having ethanol.

So do I, but... If Shell V-Power gas isn't E10 yet, it soon will be. And the pumps do not have to be marked in many states, so it may be difficult to tell when the transition occurs. We transitioned here a coupla years ago and it coaught me in the middle of some serious mpg checks. I noted the drop and thought I had a problem. It's still a top tier fuel with Techron and E10 isn't as bad as it's cracked up to be, but mpg will drop a little. As to octane, yes, the ethanol is a "real" octane booster, but E10 Premium still starts off with a higher octane gasoline before the blend than Regular. Regular starts off at 85 R+M/2 and the 10 percent ethanol brings it up to 87. 91 Premium starts at 87 R+M/2, or so, and the 10 percent ethanol brings it up to 91. In reality, I'm told, because the ethanol is blended by the distributors, "E10" can be anywhere from "E6" to "E14" in reality. I have read that ethanol does best in the Motor octane test... which is why methanol (which has similar characteristics) is a race fuel. The Motor octane test is generally the most "real-world" in the performance realm. I despise all the green and special interest politics that goes with the ethanol thing, but as a fuel, E10 isn't so bad. Unless you have a older car (about pre-'75 or even a newer carbureted car.

 

[eljefino]

I get carbon. My saturn runs with as much spark advance as they think they can get away with. (Owners manual says performance will drop above 90'F with 87 octane!) Incidentally since the ring job it consumes next to no oil. Because motor longevity is more important to the PCM tuner than performance, a single knock event gets remembered for about 200 miles and the car's a dog. With only 100 hp it gets felt. Did a water mist decarb treatment and performance is back. Knock retard memory on this car leads to a "dead spot" in RPM/load that affects the linearity of throttle response.

 

[tpattgeek]

Originally Posted By: Johnny

And, there is no reason to wait until 20K to start using the Mobil 1 in your Sienna, unless you just like the free service from your dealer.

The majority of people around here say that conventional is just fine for my Sienna with 5K OCI. I was planning on paying the difference in price and telling them to put in M1 during the free services, but unless there is absolutely no mechanical benefit to it, I may not. Thanks for the info everyone.

 

[Hokiefyd]

Originally Posted By: Jim Allen

If Shell V-Power gas isn't E10 yet, it soon will be.

Shell gasoline should already be E10. They claim that they meet the requirements of Top Tier Gasoline: http://www.toptiergas.com/retailers.html And one of the requirements is between 8% and 10% ethanol by volume: http://www.toptiergas.com/deposit_control.html So unless they're fradulently claiming to meet the Top Tier Gasoline standard, Shell gas is between E8 and E10.

 

[Loobed]

Originally Posted By: tpattgeek

Basically, my question is: People (usually people who like to go fast) sometimes say you should "get on" your vehicle to blow or burn off any carbon deposits. If that ever was true, would it still apply now? Would driving conservatively 100% of the time make a newer vehicle last longer?

I have no scientific proof that getting on the throttle will remove carbon from the engine, but I believe it will. I remember as a kid when people would make a few hard runs down the street. You could see carbon blow out the exhaust for the first few runs, then it would clear up. I do not know whether the carbon came from the engine or the exhaust pipes. I have been told that making hard runs will clear up the catalytic converters.

 

[Mullard_EL34]

Carbon build-up on the intake valves can be an issue for the new direct-injection engines. The crux of the problem is the deposits left behind by EGR crud (oil/fuel vapors, etc.) that is recirculated into the engine intake. With port fuel-injection, the metered fuel flowing into the engine washes over the intake valves and cleans-up any residue from the EGR gases. With direct-injection engines, the fuel is directly applied within the cylinders, so there's nothing left to flush the intake valves. The only real answer seems to be the installation of a catch-can, which captures the EGR fluids and only passes the gases. Of course, you then have to drain the catch-can with each oil-change, but it beats having to pull the heads to clean the intake valves...

 

[saaber1]

Originally Posted By: Mullard_EL34

The only real answer seems to be the installation of a catch-can, which captures the EGR fluids and only passes the gases. Of course, you then have to drain the catch-can with each oil-change, but it beats having to pull the heads to clean the intake valves...

Catch cans are very ineffective at preventing carbon deposits in DI engines. We have multiple examples of people running catch cans for many miles and then removing intake to find valves as bad as, or nearly so, those without catch cans. The contaminants that remain in the vapor stage still make it to the valves.

 

[tpattgeek]

Thank you everyone for all of the detailed information. I believe we all agree that, with my current 2 vehicles, reducing long-term engine wear by bringing them to high rpm's as infrequently as possible, will outweigh the supposed benefits of "carbon removal".