Foosh

I think many of us are just a little uncomfortable with the unknowns associated w/ DI. We had plenty of time to get comfortable w/ port fuel injection, and I was OK w/ just following the factory oil change recs on those engines.

I had an 07 Audi RS4 with a DI 4.2 V8 that needed a walnut shell valve cleaning at 20K miles. It was the fuel dilution due to DI in the oil analysis that caught my attention here.

Patman

I'm sure you meant C6 here.

I'm blown away by the fact that even when I try to share some good technical info in here, there are people like you and Maxie2U that feel the need to come in here and try and knock us down a peg.

joemessman

Thanks for sharing that analyses. I wonder if those of us that waited until the OLM went to 0 percent on the wet sump did any significant harm to the motor? My first oil change was at about 7,500 miles.

Foosh

I wouldn't worry about it Joe. If so, it's likely something that would only manifest itself at very high mileage points. Granted we're probably being a little OC here.

Skid Row Joe

If the oil analysis lab red flagged your Honda's oil sample with a specific advisory, then it would follow that they would do the same red flagging if something were amiss with your C7 oil sample submitted. They didn't. My conclusion is that I'm not buying that the oil lab leaves it up to you to draw your own conclusion/s, when they clearly didn't with your Honda's oil. I think you'd better get their scientific clarification on this, since your own experiences with the lab are at odds with what you told us here. At least I would want to know what I'm paying for.

themonk

WTF, who does this?

Drive your car and don't worry about schit, f'k.

Why do people in here take life so seriously, it's a car doing it's job. Do you question why the sun burns everyday and then worry about if and when it will die out?

The level of nerdiness in here is staggering.

What did you do with your C7 today and did it involve ordering Lloyd's mats?

Astrowing

The dry sump takes a long time for oil to warm up as it has so much external cooling.

Patman

Thanks a lot for adding nothing useful to this thread. If you don't like it, move along, no need for the idiotic commentary.

JerryU

I think many low milage Vettes have this issue. Worse thing for oil and engine is the rich starting air/fuel ratio blowing past cold pistons. Then not getting the oil hot enough long enough to evaporate some of the blowby that includes the main product of combustion-water! In fact the OLM takes that into consideration and shortens the time to change oil if the car is started and the oil does not get hot long enough. Especially when the Vette is just used for short trips to a local store!

With my ProStret Rod’s 502 cid engine, that now mostly is driven to car shows, I try to drive it ~25 miles when I do take it out of the garage. I avoid just pulling it out to get a ladder, then just putting it directly back! Even worse than the Vette, it has a large Holley carb and with the choke engaged it is very rich when starting and idling. The large forged aluminum pistions have sufficient clearance when cold they rattle for a few minutes as combustion temps get them hot and they expand.

Could never convince the wife that with the dry sump in her Porsche Cayenne those 1 mile trips to visit her girlfriend were not great for the car. I’m sure some who read this feel the same, and never give that consideration!

WoodyP

Someone needs to stop using the internet. I enjoyed this post. Your world must suck.

4thC4at60

You are correct in that it was my C6, not the C7- C7 has 62K on the clock. Thanks for the catch.

Not trying to knock you down....

I just don't understand oil analysis on a mass produced car that 90% of people never see 100 mph in.

As my post stated I have more than 700,00 miles in Corvettes. I have more than 300,000 miles in Porsches... and accumulated who knows how many miles in the 50-odd other cars I've owned since 1955 - including 64K miles on an old Ferrari.

Didn't mean to offend... just bewildered...

DALE#3

HA..It did,Seat belt raps too.You missed it..Here ya go

Foosh

No one here is stressing out about their oil. Doing things like oil analyses and understanding what's going on inside an engine is a hobby for some folks. I enjoyed this thread as well, but I don't do oil analyses. I appreciate the detective work involved.

I don't play golf or go fishing either, and I don't belittle those who do.

Patman

Like Foosh said, it's mostly a hobby for me, I find the info very interesting and I've learned a lot over the years. I'm not coming on here trying to tell people that they need to do it themselves, I just like sharing the information with others. It just bothers me that this thread has taken a negative turn from some of the posts.

walleyejack

Did my wet sump at 500 mi. After reading all this useful information and disregarding the useless info, i am glad id i did. Thanks for posting Pat

CTPJ

Pitman, what lab did you use to do your analysis? I have used Blackstone Labs for many years on every oil change for numerous street and racecars with multiple oil brands and viscosities. They have always provided valuable insight both historic to the vehicle (make/model and specific) and to the brand and viscosity of the oil used. Additionally, they provide an interpretation of the results in textual form (Attached is an example).

Also, I have owned a vehicle for many years with the earliest gasoline mechanical DFI engines produced - a 1957 Mercedes 300SL. DFI concerns are not a new issue and were evident (and mentioned in the car's original Owner's Manual) over 60 years ago. As a community, 300SL owners have known about, researched, and discussed DFI related issues and how to mitigate them for literally decades. The issue of gasoline dilution in the oil was much more prevalent in these old cars due to the fact that the system was mechanical (as opposed to electronic in modern cars) and remained pumping fuel into the cylinders after the ignition was turned off. This would cause raw fuel to wash down the cylinder walls after the engine was shut down. Additionally, the mechanical fuel pump (there was also an electric one) was attached to and driven off the mechanical FI pump allowing fuel and oil to mix there as well causing reduced oil viscosity. The result of these two issues was scoring of the cylinder walls at engine startup. This was one of the reasons I had to have my engine rebuilt in 2001 with 39,000 miles on it.

The vehicle also had long aluminum air intake runners that would get coated with carbon - just as various manufacturers are currently experiencing. Remember, this was an issue/problem that was observed 65 years ago... and the manufactures seemed surprised when it started showing up again. In fact, I was doing some work on my car a few years ago that included removal of the intake runners. I noticed the carbon buildup and called my engine builder expressing my concerns that this was occurring on a rebuilt engine with less than 10,000 miles. He explained that the cause was the result of valve overlap at low RPM’s and the best solution was to drive the car harder and at higher revs.

As someone new to Corvettes, I am not surprised that the same focus and conversations are currently going on especially on these low revving engines that cruise at under 2,000 RPM. What I can share is what, as a community, we do to mitigate the negative impacts of these issues in 65-year-old engines. First, we always try to drive the car long enough to get it to operating temperature allowing the fuel in the oil to vaporize. These engines have dry sumps that hold 11 quarts of oil so it takes 20 to 30 minutes of normal driving to accomplish this. Additionally, we do oil changes once a year or every 1,000 miles - whichever comes first with 5w40 oil. Even the original Owners Manual called for 2,500-mile oil change intervals. Some owners swear by diesel oil, I use Brad Penn “Green Oil” because of the high zinc and phosphorus content (this oil is not suitable for modern engines). Finally, we get regular oil analyses done to know what is going on in our engines (especially when complete engine rebuild costs more than a new Carbon 65 Edition). I realize that these procedures may not seem relevant to our modern cars but I just wanted to share that these conversations are relevant and nothing new. Hopefully, as we move away from DFI engines and move to DI/PFI engines, some of these issues will finally be resolved.

Todd

Patman

^^ Thanks for your input CTPJ! That sounds like an interesting Mercedes you have there!

The lab I use is Wearcheck Canada, it's very convenient for me because they are only a 5 minute drive from my work so I can drop the sample off directly instead of having to mail it in somewhere. And I'm very happy with the amount of information they give me (they test for a lot more things than a lot of other labs, as you can see by the numbers I've posted above) I'm not concerned about the interpretation aspect of it, as if I do have a question I have other resources to help me out.

joemessman

I just wanted to let you know I really appreciate the minutiae. I am like that regarding computers. That is how I made my living for 35 years before retiring recently. I am always interested in detailed information.

4thC4at60

Going to send you a PM.