LucV

When adding oil to my 06 C2S this morning, there was what seemed like a gas odor coming out from the filling tube. What could cause this and what should I investigate? Bad injectors?

Oil is LM 5w40 Leichtlauf, changed last November right before storage.

Car drives normally, no CEL or anything. Plugs and coils were changed about 2 months ago.

silver_tt

If you are positive the smell is coming from the oil filing tube it would be fuel dilution. Before you jump to conclusions and replace injectors you could do a $50 UOA and see what the fuel dilution % is. You would need to use Speediagnostix or a service that uses gas chromatography (GC) because Blackstone uses an approximation based on the flashpoint and that is not accurate.

Also for your comment about oil being expensive in Canada, you could look into using a shipping transfer service which is what all the Canadians I know do for parts. I don't believe oil is restricted.

ronvanr

Can too many short drives cause this? Doesn't the engine need to get all the way up to temp to reduce this risk?

silver_tt

Doing lots of short drives will increase fuel dilution because the engine isn't getting up to and sustaining full operating temperature. When the engine is run at operating temperature it will flash off much of the moisture and fuel from the oil, but you don't get this when you start up the car to get a pizza and come home in 5 minutes. Without doing an accurate oil analysis to see exactly how much % fuel is in the oil, it is anyone's guess how diluted it really is. Direct injected engines should have under 2% fuel dilution and your port injected engine should be lower than this.

LucV

I normally do runs that are at least 30 minutes but I have to admit I haven't done many that were longer than 45 lately. I had an hour long ride to see if the smell will go away. Would it take more than one or a few rides to do so?

silver_tt

30-45 mins is a good amount of time if you are on the highway and not stop-and-go traffic. I wouldn't worry too much because it's hard to tell how much fuel dilution you have just by smell alone but I would keep an eye on it. When you change your oil the smell should go away and you can see if/when it comes back. Changing your oil more frequently obviously helps and also some oils will inherently hold less fuel in suspension.

jchapura

You should diagnose a couple of ways:
-using a Durametric, look at the fuel trims (idle and driving)
-change your oil or, pull a sample, to do a SPEEDiagnostix used oil analysis

In the end, changing out the injectors, I've been told, is not a hard job but don't know first hand. I will come November or so...

LucV

Thanks for the input. I change the oil right before storing the car in November, then it's out in April. I drive about 5000km/year. I change the oil before storing it. As far as I can tell, this is the way to go:

Petza914

Correct, store the car with fresh oil. Oil becomes acidic with use and acid eats metal.

LucV

I'll take a drive tomorrow with an OBDII dongle attached to check the fuel trims. However, long term on bank 2 is at -2.3% while the engine is turned off (cold, parked for 3 days). Is that normal?

jchapura

@LucV Take a look at this thread https://rennlist.com/forums/997-foru...le-levels.html .

LucV

Thanks for the link. I took a one hour drive and long term fuel trims when the engine was warmed up was between what was acceptable in the video (+/- 3%). Bank 1 was between 0% and -1.6% while bank 2 between 0% and -2.3%.

I may have taken shorter trips this year now that I think of it. Sometimes 20 minutes to the store, cool down for another 20 and then another 20 minutes drive. I did bring up the car to temp but perhaps not long enough. Usually I try to take longer drives before doing errands but I've been super busy this summer. I'll make sure to improve that.

Since I'm doing an oil change in 2 months, should I do one right away and again early November or keep it that way? I'll be doing a UOA at the next oil change nonetheless.

jchapura

I'm the curious type (for my own situations), engine oil is relatively cheap compared to an engine rebuild, and your location's likely overall lower temps would be an aggravating factor for bore scoring so if it were my car, I'd change the oil now and also prior to winter storage. I'd also use SPEEDiagnostix for the UOA because of their gasoline content testing method.

Another path might be just to change the oil after changing all the fuel injectors. The OEM parts are not expensive and the change-out seemingly can be done by a moderately experienced DIY-er.

Another path might be to try to clean them with a high-PEA fuel additive. I think this might be a bit of kicking the can down the road.

LucV

Do you think the fuel trims are problematic? If not, wouldn't it be overkill to change the injectors? If I do change them and the oil, I assume I'd do the UOA during the oil change right before storage?

jchapura

In and of themselves, I don't think the fuel trims are problematic but they are coupled with another symptom - gasoline in the crankcase. One or more of your fuel injectors might have a borderline spray pattern that's contributing to washing down the cylinder wall. I still lean towards doing the "extra" UOA right now to confirm the level of crankcase oil contamination.

I've not ever tried this myself but definitely would if the situation suggested it - a non-oil-change sampling of the oil. Somewhere there's sold a way to "suck" out the oil. So, drive the car to get the oil mixed up and warm, then do the sampling (but not off the very bottom/sump plate - somewhere mid-level).

An alternative to sucking up the oil, but be prepared for a bit of a mess, do the car driving, note the oil level, then gingerly remove the oil drain plug, let it run for 3 seconds, take the sample, replace the oil drain plug, top off the oil to the previously noted level.