Excessive idling, what effect does it have on oil?

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Staff member
May 27, 2002
Guelph, Ontario
Lately I've been getting stuck in a lot of bad traffic jams (idiot drivers getting into accidents everywhere lately!) and was wondering as I sat motionless in my car on my drive home, what effect does all this idling have on my oil? It took me about 30min to travel less than a mile, and this has happened at least 3-4 times on this oil interval. Will this excessive idling cause more fuel to be put into the oil?
Other than bring the oil temps up I can't see much harm in the fact that you are running your engine longer than what miles are being put on the oil. Taxi Cabs and Police cars do a tremendous amount of idling. Heck and most of them don't use synthetic. Go figure.
I now turn engine off at lights etc. Idling not good for an engine.. And never idle an engine to warm it up, all that raw fuel from the rich idle mixture washing the cyl walls.
If traffic stopped totally dead for long periods I would definitely shut the engine off, but it was moving a little bit at a time. I never idle the car longer than 15sec on a cold start before pulling away, even in winter. I drive extremely gentle during warm up though, with this car being automatic (and having a lot of low end torque) I have no problem keeping the rpms below 1500 for the first few minutes of operation. I truly think that this is an extremely important thing for long engine life (although I knew a guy with 250k on a big Olds who would start up his car cold, rev the engine two or three times, and then blaze out of the parking lot at work like he was going to a fire!) The only time I drive hard on cold oil is sometimes at the dragstrip if I have had to wait 60-90 min between runs. That worries me sometimes, driving the car at full throttle with the oil probably no hotter than 160F.
patnam You should get yourself a magnetic oil pan heater. I bought one a few years ago at the parts store for around $15.00 that i stick to the underside of the oil pan. I use it to heat the oil in my boat when it is cold out. It says it will heat it to 200+ degrees.
John, that sounds like a great idea! It would definitely help me out, because with warmer oil, but a cooler top end on my motor, I'd run quicker quarter mile times for sure. I'm sure my cold oil is lowering my power output by a couple of horsepower (maybe as much as 5hp if the oil is really cold)
Patman, does your car have an oil cooler like my Impala? If so, the oil will rarely get over 210-220 range. Actually it will normally stay in the 180-190 range. I would not worry about occasional drag racing hurting your engine. As long as the oil is not very cold, it should be flowing fine, that's the beauty of multi-vis oils. [ June 13, 2002, 10:13 AM: Message edited by: VaderSS ]
My car was supposed to have the oil cooler with it, as in the 1995 Firebird brochure it states that the optional 3.23 rear end ratio automatically comes with the oil cooler, yet mine did not get it. A few others I know with 95s with these 3.23s also said they didn't get the cooler either. From what I have gathered though, this oil cooler is very problematic on the f-bodies, it is prone to leakage, and people report that the longer oil filter ends up sitting down too low as well. So in the end they say I'm better off without the oil cooler.
We too have problems with oil cooler leaks, usually at the lines going to the radiator. People also say that we would perhaps be better off without it, since the oil runs so much cooler than normal, but I've never heard of anyone pulling it off, unless for header clearance. These LT1s easily make 200000+ so I don't really think it's an issue.
That is true, the LT1 is durable! There was a recent thread in CamaroZ28.com talking about mileage and one guy mentioned he saw an LT1 with 300k on it! So if I keep my LT1 long enough, and practice what I've learned on here so far, I should see some pretty high miles myself someday! [Smile]
That is one of the things I love about synthetics, run em long, and still have a cleaner engine than with conventionals. Many of the people who run Mobil 1 in thier Impalas still change the oil at 3000 and absolutely refuse to believe you can run it any longer. Heck, my oil is still amber at 3000, why would i change it? Computer controlled electronic fuel injection is undoubtedly the single most important innovation when it comes to making engines last so long. Absence of fuel wash from the accelerator pump of a carburettor and precise fuel metering really helps. I bought my Impala in Denver CO. It was 12F at 5000 feet altitude the morning I drove it home. Started on the first crank and had full power immedietely. Then I drove it to Houston and Sea Level. Same great manners and runs even stronger. Try that with a 60s muscle car. [Smile] Oh how I love modern cars!
There are plenty of Impalas at over 200k, using no oil and still running 14s with the cheap mods. I've heard of caprice taxis with L99s(4.3L version of the LT1) making it to 500k, though they are pretty well clapped out by then.
I think the conventional wisdom of 10+ years ago was that excessive idling caused your crankcase oil to become saturated with fuel. With today's fuel injection systems, however, I believe that is no longer much of a concern.
Originally posted by VaderSS: There are plenty of Impalas at over 200k, using no oil and still running 14s with the cheap mods. I've heard of caprice taxis with L99s(4.3L version of the LT1) making it to 500k, though they are pretty well clapped out by then.
Another trend I've noticed is that 90% of the high mileage LT1 guys have run basically nothing but Mobil 1 oil! Of course, this would be mostly the Advanced Formula Mobil 1 and TriSynthetic Mobil 1 that they have run so far. Another point of note is that any of them who had run nothing but M1, will say that if they've taken the engine apart (to put in roller rockers or a cam, etc.) that the engine is very clean. I know my LS1 was super clean inside when I pulled the valvecovers off around 25k to check the pushrods. I ran nothing but Mobil 1 in that car too.
sprintman I now turn engine off at lights etc. Idling not good for an engine.. And never idle an engine to warm it up, all that raw fuel from the rich idle mixture washing the cyl walls.
With a good fuel additive like Schaeffers 131 or lucas(don't know which)... You don't have to worry about washing the cyl's. One of the most problem areas of fuel dilution in the oil is the sulphur which is become less in fuel than before due to epa standards, but with schaeffers 131 or lucas, it will nuetralize the sulphuric byproduct produced by the fuel. The other thing is since sulphur is the lubricating property of fuels, and being reduced as such, a good fuel additive will replace this with a lubrication property into the fuel thus reducing any problem with the wash down effect due to excessive idling concerns.
Wondering if synthetic suffers any less than conventional w/ the idling. I opten spend 20-30 minutes stock still idling while The Missus does errands. Usually have the kids in the car and the AC on max so I really can't shut it off due to the ambient temp.
I don't think that EFI and mixtures are the only thing that causes fuel dilution or oil degradation and, thus, cannot completely eliminate it. When idling, there's almost no load on the engine (AC excluded). This can lead to less ring seal because of "low" cylinder pressure. This may mean that there's a lot more blow-by into the crankcase when idling. This can carry some fuel and all of the other acid-causing combustion nasties into the oil in higher amounts than when ring seal is better. I suspect that during this period more "crud" would also be getting fed back via the CCV/PCV system than in normal operating conditions like highway cruising. I would also expect idling to promote carbon buildup since it is the polar opposite of an "Italian tuneup" in the hilly twisties. Idling is probably always a bad idea, modern EFI or not. Modern EFI can only watch for unburned fuel in the exhaust gases, not the crankcase, and doesn't account for all of the other negatives. In some situations it's unavoidable, and even cars who do it a lot can make it to high mileage. It may come down to your OCIs, your oil's ability to combat contamination, and your general maintenance regimen (fuel quality, fuel system cleaners). Another factor of potential concern is whether your particular engine model was designed to provide sufficient lubrication pressure/volume for extended periods of idling. I would not make the assumption that this is in the design criteria of every engine manufacturer like it would be when designing vehicles used for taxi and emergency response uses. In the situation describes by the OP there will be a LOT of heat soak and very little airflow. Despite low engine load temperatures could skyrocket in parts of the oil (and water, depending) system.
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Obviously police and taxis prove that idling has little to do with longevity. But this is EXTREMELY platform dependent. Our equipment runs off the engines of our vans at 1500 rpm most of the time, and we specifically do not shut them off unless they will sit for more than 10 minutes. They burn less than 1.5 gallons per hour while working! We routinely run these rigs 250k miles and have one in daily service with over 400k miles! Seems like it means virtually nothing to our rigs to idle a while.
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