LJC7

I am a new 2016 Z51 Corvette owner and certainly want to do what is best for my car. The owner's manual in a number of places recommends Mobil 1 as the preferred engine. It also states that the engine oil life system should be used to determine when to change oil. When I got the 500 mile initial oil change, I got the car back with a 4000 mile recommendation for the next engine oil change. When I questioned why this was different from the manual, the service manager said that they now use a synthetic blend rather that Mobil 1 at the dealership and that the factory fill is now a synthetic blend. I questioned why that was not reflected in the manual. He eventually contacted someone he described as a "Corvette engineer" at GM and said the engineer confirmed that factory fill is now a synthetic blend which would have a reduced service life. At my insistence, they drained the engine oil and replaced it with Mobil 1, but still said I should change it at 5000 miles. Can you clarify what the correct engine oil should be for a Z51 and how often it should be changed? Thanks.

-HAIRBALL-

Just stick with Mobil 1 but in all honesty, any dexos approved synthetic is fine. Just follow the computer and it will have you changing it every year or "around" 7500 miles (which ever comes first) as it also depends on how you drive it. I change mine every May and I average about 5k a year.

sunsalem

Only 2 things are necessary to know regarding oil changes:
1) Use Mobil 1.
2) Change whenever the car's computer tells you to.

Patman

Anyone following this practice will easily get 200-300k out of their Corvette's engine (and in reality there are very few people on here that will even hit 100,000 miles on their C7 before they trade it for a newer Corvette or other sports car anyways)

sunsalem

Very true.

Glen e

This is getting better reviews than mobile 1 on the Camaro and Corvette sites recently… Still available at Walmart, still a good deal

vbdenny

You do not want the blend which is dinosaur oil mixed with synthetic. GM says full synthetic Mobil 1. 0-20w I think. Should go about 10,000 on an oil change to zero. Maybe 7,500 at 30%.

JerryU

Glad you stuck to your guns! Use 5-30 Mobil 1 (or at least another full synthetic.)

He was feeding you a bunch of bull!!

He probably bought the cheapest blend that met the GM dexos spec, which is fine for most of the cars he services (or at least acceptable!)

Mobile 1 is used at the factory.

Second, even if a dexos blend the OLM is all you need to use! Anything more is for him to make more money when your free fills are finished.

If he actually believes his own bull (which I doubt) he is just not smart - along with dishonest! Thought Jiffy Lub were the only folks still putting on change at XXXX stickers!

SIDE BAR:
They no doubt have a 55 gallon drum of the cheap blend in the oil change bay. That is where their mechanics helper (who could have been flipping burgers the week before) pulls the trigger on the fill gun and oil is pumped in. He probably also does not check the level after filling (which it clearly says to do in the the Service Manual- it notes the fill table is only approximate and the fill level is what is important.) . Especially with dry sump like yours since he would have to:
1) Run the engine to get the oil past 175 F
2) Wait 5 minutes for the oil to drain down from the tank baffles to check the level.
3) But not wait more than 10 minutes or excess oil will drain back to the oil pan and he's get a false reading. No just going on a coffee break! In fact for fun checked after the car had sat for over a day and it was >5 quarts low!

Suggest, you should check the oil level per the manual, and as I just defined. If it's over MAX you have a chance of oil burping with the air that pumps with the oil from the pan. Then you'll get oil in the air intake above the filter. It will then run down soak the filter and you'll see in drip on the ground! It could also contaminate the MAS (Mass Airflow Sensor) and it could need replacement.

From a number of posts, folks who come back from that 500 mile change that is ONLY to stop oil foaming and oil dripping from the air cleaner-have just that happen from an overfill! Unfortunately there are other mechanics helpers working oil change bays!

Also if the mechanics helper isn't careful it will overfill and pill over the oil intake port. Unfortunately tough to clean it from the back of the dry sump tank when it runs down. That is where the cabin air filter is located behind a not very tight piece of plastic. Folks have posted smelling oil for several weeks after a dealer fill. I change my own oil and have from the first in my Z51 C7, free was not worth the risk for me! I did the same in my Z51 C6 and have never smelled oil. But I must pour slowly or it will come out. I also put an old towel around the fill opening-"just in case."

NOTE: the OLM is a very sophisticated algorithm that incorporates, engine rpm (much better than miles as an indicator,) number of starts, oil temperature after starting to be sure the water in the blow-by in a cold engine has a chance to evaporate) as frequent short trips will shorten when it says to change, etc The C7 also incorporates time, so after 12 months it will say to change if it hasn't said to change sooner. Just do what it says and you'll be fine

rmorin1249

I believe 5W30 is the correct weight unless you are tracking.

CSevenGS

I use Royal Purple. Mobile 1 is no better than it and I've always used it on much higher horsepower engines with no issues. Not using Mobile 1 doesn't affect your warranty, only using oil not on the approved list.

Bill Dearborn

How many miles a year do you drive the car? If it is less than 5000 then the question is moot since the OM states the oil should be changed once per year.

If you put more on than that you should go by the OLM. It adjusts the oil life remaining on how you use the car not just miles. That is also why you need to use Mobil 1 as GM Recommends in the OM and a TSB that is posted on the forum.

The OLM is calibrated based on using Mobil 1 and will give a wrong indication if you are using the car hard and don't have Mobil 1 in it. Mobil 1 will stand up to high rpm, high temperature usage better than the blend. However, it will shorten the time between oil changes if you use the car that way. The problem with using the blend is it will not shorten the time period quick enough. On my C5 and C6 Corvettes I have seen the oil life drop quite a few percentage points over a day's time while attending track events in the hot summer months.

Bill

dbaker

As someone mentioned earlier....any full syn oil that meets the Dexos1 spec should be fine.This is usually shown on the back label of the oil container.

Mobil1 is a good oil and GM and Mobil have a long association.They both have profited well from that association.It's the same kind of deal that Ferrari & Pennzoil had.

Have a look here.It may help you decide.
http://www.bestproducts.com/cars/par...car-motor-oil/

For my other cars,the OCI is 5k miles.For my last 3 Vettes,it's 5k miles or when the OLM is 10%....whichever comes first.

I too have a Z51.Enjoy!

\db2

JerryU

Comments about which oil, should also mention cost. I see some being mentioned that are $8/quart.

My Oil Experience: Been using Mobil 1 since about the first time it was commonly available in 1974. The Datsun rep recommended I use it for the dashpots on the Hatachi SU's in my 260Z! Solved that problem. Read about what I bought and tried it in my modified Corvair. Despite adding finned extra capacity aluminum oil pan and finned valve covers the oil ran about 300F in my modified car. It formed scum visible on the oil intake tube. Mobil 1 solved that issue-no more scum!

Have been using it ever since. All of the "true full synthetics" changed in ~2000 when Mobil lost a suit to Castrol who sold a highly refined "dino oil" and called it synthetic. All the companies had to change as it cost about half to produce. All prices dropped.

My last two oil changes I bought 5 quart jugs of dexos approved 5-30 Mobil 1 at Walmart for $22. There have been $12 Mobil rebates/quart (two allowed. That's ~$2/quart!

Why spend more when I could probably go much further but my changes are at 12 months!

I have been looking for an oil that reduces "coking," and issue in DI engines. Considering the intake valves run much hotter than any oil breakdown, no such animal. Until there is I'll stick with Mobil 1.

rkhegler

Go by the book. Whatever your owner's manual states. No exceptions.

Also, from another thread:

Chevette!?!?

Mobil 1 synthetic is the best,..........However, The blended oil should be used for the initial break-in(10k miles or so). The full synthetic oil is just too slippery (viscosity) to properly break-in a fresh engine! Your new engine needs a certain amount of friction to seat all of the parts the right way. This applies to all engines during break-in. After that, feel free to switch over to full synthetic. You'll get years of
smooth running and reliability that way. Hope this helps. I have an '05 V-8 truck with over 150k miles on it and you can barley tell it's running at idle.

Patman

It's not necessary to run a new engine on blended or conventional oil, the Corvettes have had M1 as the factory fill for a very long time and that has never hindered the break in process whatsoever. Contrary to popular belief, synthetic oil is not "more slippery" That's an old wives tale that just won't go away.

iclick

I've used RP for the past 20 years and would use HPS in the C7 except it isn't Dexos approved. That wouldn't affect the warranty unless I had a catastrophic engine failure and GM decided to play games with warranty and blame the oil. To be safe, or maybe chicken, I've been using M1 which is much cheaper and is an excellent product. In a street engine run like mine (rarely stressed), it will be fine.

Their Dexos product without their proprietary Synerlec additive may not be much better than M1, according an RP distributor I know who has a history of being honest with me. What drives me more toward M1 is their bi-yearly rebate, usually surfacing every spring and fall, where you can buy five quarts of M1 and get $12 back. Another reason is that I'm frugal (i.e., cheap bastard). Buy a 5-qt. jug from Walmart for ~$24 and you'll get it for about $2.40 per quart, and you can use the rebate for up to 10 quarts per offering. In six months, do it again, etc., ad nauseam. For the past three years I've been taking advantage of this rebate and I now have ~25 qts. stockpiled, even after using it in my truck for that period (C7 is still on the free oil changes) and when the next rebate comes again soon I'll buy another two jugs. Can't beat that with a stick.

iclick

FWIW, a dealer parts manager told me about a month ago that the Dexos blend was being phased out in favor of the GM Dexos1 full synthetic, and that their dealership changed over four months ago. Since Exxon-Mobil makes the GM oils I would imagine it is identical or very similar to M1, and I wouldn't be averse to using it.

When I had my C6 and had one free oil change, for which dealers at that time were only authorized to use the blend, I did some research on it. What I found was that it was a quality product with a good additive package, is made by EM, and I used it for that one free oil change--but switched to M1 once I started changing it myself.

iclick

I've seen quite a few articles on this subject over the years in the automotive press and they generally agree with what you say. In a C&D article some time ago they took a neutral view and suggested using fossil oil for the first change as a precaution, as short-term use of a quality brand (I always used Castrol GTX) won't hurt the engine in any way. In the past I always used a fossil oil for the first oil change, then switched to synthetic--but for the C7 I just used M1 as per the free oil change offering from GM. The rings should seat almost instantly, certainly in the first 50 miles, and I would think that would be the only thing that might suffer from any increased lubricity from a synthetic product, if indeed that is even the case.

iclick

FWIW for those with new cars, that reference doesn't mention the 2017 MY, but the attached document does. It's confusing since it only mentions 2017 cars in one place, avoiding that YM in other areas of the text. Some dealers might balk at using it as an edict to use M1 in C7s.