engine oil

[burkeybb17]

I have an older car with approx 94,000 mi. My guess by the first oil change I did when I got it was that it wasn’t really taken care of. My question is I noticed that the old oil coming out of the engine smells of gas. How does this happen and at what point does it pick up this smell? I’m assuming its from the dirt in the block itself…..anyone care to expand?

Topic

[dreamer2355]

The smell of gas could be from blow-by gasses or down from constant ‘short trips’. I would take the vehicle for a spirited drive often so the oil will get up to operating temperature and burn off some of the contaminants and condensation if the vehicle is primary used as a grocery getter.

You will learn a wealth of information from this website regarding automotive fluids –

http://www.bobistheoilguy.com/forums/ub … p?ubb=cfrm

[cb7ftw]

When I got my car with 250,000 miles on it, the oil looked bad too. Here is how I de-gunked my engine. Put 1 quart of automatic transmission fluid, and 3 quarts of oil. Then drove it around for a few days, and did another oil change. Use good oil filters.

[valde]

Using automatic transmission oil or any other solvent in engine oil might remove a clump of sludge witch might block an oil channel and then completely destroy engine. Not to say that is likely but take it into consideration.

[EricTheCarGuy]

Quoted From dreamer2355:

The smell of gas could be from blow-by gasses or down from constant ‘short trips’. I would take the vehicle for a spirited drive often so the oil will get up to operating temperature and burn off some of the contaminants and condensation if the vehicle is primary used as a grocery getter.

You will learn a wealth of information from this website regarding automotive fluids –

http://www.bobistheoilguy.com/forums/ub … p?ubb=cfrm

I’ve seen this a lot so +1 on this post. Also resist the temptation to use synthetic oil as you it will probably cause just about every seal in the engine to start leaking and you will most likely end up with an oil burning problem as a result. Just use the recommended oil for your engine as listed on the oil cap or in the owners manual and change it at regular intervals.

[WDHewson]

I used to be involved with a group measuring fuel dilution of engine oils. But this was a long time ago in the carburetor days.

In Summer with hot running, fast engine warm-up, and minimal choke-on time, the engine oil was averaging about 3 to 5% of gasoline by weight. In winter with shorter colder trips, cooler engines, and long choke-on times, it was not unusual for the oil to be 10 to 12% gasoline. Yes, really, 10-12%.

Not much harm was done to the engines with 10% fuel dilution, but we did feel we noticed a bit more cam and follower wear. But in these older days, cams and followers were all sliding and not rollers as in modern gasoline engines.

It was much harder to measure fuel dilution of engine oil in Diesel service, as the heavy ends of Diesel fuel overlap with the light ends of lubricating oil, so you could not distinguish oil from fuel.

My guess is that computer control of gasoline mixture in our present cars will give dilutions a bit less than in the carburetor days.

But the bottom line is, get some fresh oil in there and change it at reasonable time/distance intervals.

[Trcustoms719]

Change the oil with the right oil for your car as said above, and you might want to change it around 2,500 miles for the next few oil changes then you would move up to 3,000 miles.

[Third Gear]

Whenever I’ve done used oil analysis, the lab likes to see fuel dilution less that half a percent.

If the engine wasn’t well maintained to begin with, synthetic oil or engine cleaners can cause slow leaks to become more noticeable because they remove all the build up, crud, etc. I like Castrol GTX and Mobil Super for convential oil.

[WDHewson]

I was curious about the modern situation for gasoline dilution of engine oils.

A fairly convincing publication says that more than 4% gasoline in the oil should be considered abnormal. So it looks like things haven’t really changed from my 30 year old data of 3 to 5% mentioned earlier. So much for the precise modern fuel injection.

I’ll try to copy in a link, but I seem to have problems inserting photos and links in this site. Still cannot paste, so search thermal-lube.com, then under publication and look for the article on fuel dilution.

[killman]

Do check out Bob is the Oil Guy forums (aka bitog) for any oil info. Used oil analysis is a great way to tell the condition and find problems with any engine. Want to know if your GM 3100/3400 lower intake manifold gasket is starting to leak 10-15-20k miles before you could find it normally (or it trashes the engine). Do an used oil analysis. Want to know if there are bearing wear problems or problems with the PCV system. Do an used oil analysis.

Fuel in the oil is an older problem that nearly had disappeared but has returned with a vengeance. The auto makers have rushed into production the direct injection gas engines without properly testing them so the public are the “beta” testers. The biggest problem is fuel dilution in the oil so bad that 4% by 5k miles is common unless driven 90% or more on the highway. Short trip UOAs are a nightmare on these engines. Also without fuel “washing” the stem of the intake valves deposit buildup is a problem similar to worn intake valve guides/seals on older cars. Toyota and Audi are using an “extra” injector or two to supply some gas into the intake at low speeds to clean the intake valves on newer designs.

[EricTheCarGuy]

I’m learning lots from this thread thanks for posting everybody. As to ‘modern’ engines being better than their older counterparts the truth is that the design of the base engine is still the same so until the engine is fully warmed up the clearances are a little ‘loose’ so even with a modern engine with better fuel controls you will still see fuel in the oil as this I believe is an unavoidable fact because the basic design of the engine has not changed. I see this condition pop up a lot especially with cars that don’t get driven often and fully warmed up (I’m going by the ‘smell’ of the oil when I change it). To help counteract this condition the newer fuel maps monitor coolant temp much more closely and will set a code for a thermostat whereas the older systems did not have this capability.

[wilson3707able]

my 1993 toyota mr2 with a 2.2 engine and has 107,000 miles. I started using synthetic oil when the car had about 80,000 miles and since then it developed two leaks (valve cover gasket and oil pan)i fix both. i still use it because i heard good things about it. i used synthetic penzoil 10w-30 (i can’t find 10w-40) and i change it every 3,000.
Now guys, my question is should i stop using this synthetic oil? and what is the best oil and weight for this car. i intend on keeping it for a long time.

[EricTheCarGuy]

Quoted From wilson3707able:

my 1993 toyota mr2 with a 2.2 engine and has 107,000 miles. I started using synthetic oil when the car had about 80,000 miles and since then it developed two leaks (valve cover gasket and oil pan)i fix both. i still use it because i heard good things about it. i used synthetic penzoil 10w-30 (i can’t find 10w-40) and i change it every 3,000.
Now guys, my question is should i stop using this synthetic oil? and what is the best oil and weight for this car. i intend on keeping it for a long time.

I think you should start by extending your oil change interval if you’re going to continue to run synthetic because now your just throwing your money away. The only real benefit to synthetic that I can justify for an older engine like yours is the ability to extend your oil change intervals to 7-10K. I believe they write something to this effect on the bottles themselves.

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