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gas in oil

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Old Aug 10, 2012 | 03:06 PM
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Question gas in oil

anybody have gas in oil problems ??????????
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Old Aug 10, 2012 | 03:21 PM
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When did you last change oil? Do you do a lot off short trips?
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Old Aug 10, 2012 | 03:36 PM
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I thought it was kinda normal. All my Rx's had a gas smell to the oil.
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Old Aug 10, 2012 | 04:01 PM
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How does gas get into the oil?

My only experience with that was in the old days of mechanical fuel pumps, if the diaphragm leaked.

Ken
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Old Aug 10, 2012 | 04:09 PM
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Blow-by?
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Old Aug 10, 2012 | 04:25 PM
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It would help if you explained your situation a bit better.
What makes you think there's gas in your oil? What year is your car? How many miles? Any mods? When was your car last serviced?
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Old Aug 10, 2012 | 04:42 PM
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Blowby in a piston engine is pretty much the counterpoint to rings getting lubed by crankcase oil. So in a rotary it would be past the side seals, right? The ones some of us never think about because of our fixation with the tip seals.

So to add to Timex's anxiety it could be a bad side seal.

Ken
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Old Aug 10, 2012 | 04:49 PM
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I don't see whats to worry, I've logged tons of miles in 3 different Rx7's, all had the fuel smell and they all survived me somehow. This is my fourth, it's the newest rotary I've owned and it has the same smell as the old ones. I think part of it is from not being able to change all the oil out when doing a simple oil change.
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Old Oct 19, 2018 | 12:26 PM
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Old thread that I'm reviving as I couldn't find another one on the topic. "gas in oil" is a tough one to search on it seems as it pulls up so many posts.

Anyway, today I got an oil change on my 2005 RX8 and the mechanic said there was gas in the oil and asked if I was having starting problems to which I answered no. I had been having low power issues below 4000rpm but just swapped out my coils and it fixed that problem (and starting does seem a bit faster too).

Should I be worried about gas in the oil? I don't have any CELs, power, idling, or starting issues. I do find that the exhaust is pretty smelly but to be honest I can't tell anymore if it's always been like that as our other primary car is an EV (BMW i3)! The mechanic said the exhaust was really smelly too but he could not find any leaks in the exhaust system, and had no explanation for it. This was just Midas and not any special knowledgeable place about rotaries.

Oh, the car has 105K km on it, original engine, and I'm original owner. No mods to speak of.

Thanks, ...Roger

Last edited by rcolbeck; Oct 19, 2018 at 12:37 PM.
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Old Oct 19, 2018 | 01:00 PM
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When you swapped the coils did you also change the spark plugs?
If your car spends a lot of time cold idling, then yes, you would have gas in the oil. It's not bad, and everybody has some quantity of gas in the oil (on any car). Problems start when there's more than a fraction of a %. One thing you could do is get your used oil analyzed by someone like Blackstone labs.

As for the exhaust smelling rich: on cold start up yes, but when warm it shouldn't smell. There could be a few causes: old spark plugs, rich condition due to vacuum leak, failed catalytic converter, etc. I'd give those items a review to confirm/deny any potential problems.
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Old Oct 19, 2018 | 02:26 PM
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Originally Posted by Loki
When you swapped the coils did you also change the spark plugs?
If your car spends a lot of time cold idling, then yes, you would have gas in the oil. It's not bad, and everybody has some quantity of gas in the oil (on any car). Problems start when there's more than a fraction of a %. One thing you could do is get your used oil analyzed by someone like Blackstone labs.

As for the exhaust smelling rich: on cold start up yes, but when warm it shouldn't smell. There could be a few causes: old spark plugs, rich condition due to vacuum leak, failed catalytic converter, etc. I'd give those items a review to confirm/deny any potential problems.
I was lazy/cheap and did not swap my plugs as I had done them last year. I did have a flooding incident though this Spring when I started it up (I don't drive the car in the winter so it had been sitting a while). I did the normal procedures and got it started after an hour or so. I guess I probably should swap my plugs too.
I think it still smells when it's warm but I'll keep checking. I did about 15minutes of high rpm driving this morning on the way to work to see if that helps clear anything out. Unfortunately the used oil has now been chucked and I wasn't planning on changing the oil again this season before I put the car away for winter.
I'll do the visual check on the CAT at night to see if I see any glowing unless you can suggest a better way. It wouldn't surprise me if the CAT is bad given there is 100K km on the car and having driven it with crappy coils for a while.
Thx
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Old Oct 19, 2018 | 03:12 PM
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Bad cats kill engines, so I would remove it from the car and inspect inside.
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Old Oct 19, 2018 | 03:16 PM
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If you are just hot idling, you shouldn't smell anything with a cat, other than maybe a very faint sulfur smell depending on the gas you use.
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Old Oct 19, 2018 | 05:06 PM
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If your cat is bad you will get a smell all the time
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Old Oct 26, 2025 | 03:32 AM
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Daily driver here, and weather getting colder in the North. Late summer, I set the oil-fill level well below the max markings on the dip-stick to prevent S1 from chocking in it's own oil on high revs.
I checked the oil level after few months, and distinctive smell of gas/fuel in oil is present. The oil level was above the max markings and I suspect high quantity of fuel in oil.
Changed the oil, about 4 liters came out and put 3 liters new back in to be around middle on the dip-stick markings.

Is there a simple way to check if my injectors are leaking while in park?

Long term and short term fuel trims combined seems to be on the plus side more than negative. Intake to maf is not standard, cold air intake.
Also the engine temp is on the low side due to my fan setting around 80-86 degC. I mostly drive 10-15 km per day few times.
Eliminated the CAT warmup cycle and looking into running as lean as possible on cold engine to prevent over fueling and carb buildup.

How normal is it to have noticeable amount of fuel in oil in RX8 on Autumn to early winter season?
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Old Oct 26, 2025 | 07:29 AM
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Do you spend a lot of time in traffic or idling? 10-15 sounds like short trips, you're spending a lot of time warming up. Could be the culprit.
How did you eliminate the cat warmup?

Last edited by Loki; Oct 26, 2025 at 08:35 AM.
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Old Oct 26, 2025 | 09:31 AM
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Originally Posted by Loki
How did you eliminate the cat warmup?
Pushing the right buttons in the ECU...
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Old Oct 26, 2025 | 11:19 AM
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Your fuel trims there are 0.0 which sounds like system not ready. What are the fuel trims when it's warm and idling?
Which intake is on there? Most intakes cause airflow instability and MAF issues, shich could lead to over fueling.

I don't think it's an injector problem, even if it leaked, the fuel wouldnt make it into the oil without pressure.

Last edited by Loki; Oct 26, 2025 at 03:57 PM.
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Old Oct 26, 2025 | 02:55 PM
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Trims are 0 because cold starts use open loop fueling for as long as many conditions prohibit closed loop fueling.
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