Hi, a friend of mine owns a 91 dsm.

We did an oil change and the oil was brown, almost the color of mud. There was no coolant in the oil, however it did smell like gasoline. The car is tuned. There is no oil in the coolant, we drained it and it was fine.

It is rich during cold idle.. I mean like in the mid 10's.

Any idea if this is a 'bad' sign? Or if its just fuel and we need to change the oil more often?... Could it also be because of a less than satisfactory PCV system? (its stock pcv to a open catch can..). The catch can never really accumulates much.

I know this is a dsm guys but could you help us out? My 90's oil always looks fine when I change it, but again.. My AFR's are fine during cold idle (never richer than 13.5:1 under vac).

 

Just sounds like used dirty oil to me... and clean up that idle !!

 

Oil is usually blackish when used, light brown when lightly used. Mud-color can be from a bit of coolant being mixed very thoroughly. If left to sit long enough, the emulsion should seperate into oil & coolant.

If it also smells like gas, the rings are probably taking a crap, and/or an injector or two. 13.5:1 vs 10.5:1 is about 30% more fuel. The low piston speed at idle can let the gas puddle enough around the rings to "wash them out", basicly displace the oil & wear them out.

I'd try a coolant system pressure test, and definately do a compression test. An extended leak down test is the best way to test for ring damage - check leakdown at various piston heights to see how the whole bore is doing.

 

yeah, the gas-smelling is probably because there is gas in the oil.

tune that idle out, and keep an eye on it for the next few oil changes. and definitely do a comp/coolant pressure test.

 

Alright thanks.

The car did sit outside for probably ~4months, maybe got started up 3-4 times to be moved, and everytime there was the rich rich idle.. Its much worse in negative temps, but the car was tuned in the warmer weather so its great it even starts with the 1000cc injectors. It was due for an oil change regardless... There isn't 'excessive' fuel, but enough to smell it.. I will do a compression test as well as a leak down. See if anything is leaking into the coolant system.

The car NEVER had a overheating problem, never went though coolant, and never got air in the coolant either.. So im hoping this isn't a coolant mixing with oil issue.

When we first cracked the drain plug to drain the oil, we did notice some white come out at first, but.. It wasn't white like coolant, this was a just a very quick spirt of a white liquid, but it was VERY white, maybe 5-10ml came out, and than the rest was just straight brown oil. We ran close to straight water in this thing as well, maybe a 80/20 mix.

A compression/leakdown test will tell me what I need to know, so no worries for the time being, it is what it is..

My friend has a 97 neon with a turbo 2.4L in it, and he has the same problem, always brown oil, even when it was NA the oil was still brown. He has just never worried since hes a budget guy anyways and cant afford to do anything about it.

Thanks.

 

We just did a leak down on the cold motor. Results....

Cyl #1 - 7%, Cyl #2 - 9 %, Cyl #3 - 7%, Cyl #4 - 5%.

I honestly couldn't even hear where it was leaking from.. But its so minimal its nothing to worry about. I can't do a compression test because there's no oil in the motor! You guys think I could still have trouble with compression even though I got such great leak down numbers for such an old motor?

There is no signs that compression could be down.

What do you all think, motor seems healthy.

 

Are you using a breather or a proper PCV system? A PCV system would help keep your engine cleaner than a breather. I'm not sure why the oil is brown though. Is this something that keeps happening or did the oil only look this way during this one oil change?

 

It was brown the last 3 changes.. I tell him to change the oil at sooner intervals instead of every 4-5000km. Maybe ever 2-3000km and see how it looks than.

There is vacuum assisted pcv, just breathers.

 

I like doing occasional "evaporation runs" when the car sits for awhile. Just drive it around get it to operating temp to make sure all the condensate/fuel burns out