I own a 2001 C-5 Corvette using Mobil 1 synthethic 5W-30 oil. How often does it need to be changed ?

Question

Some people say that synthetic oils don't need to be changed as often as regular motor oil, which was between 3500-5000 miles. My C-5 Corvette uses Mobile 1 synthetic oil. Some people say I should change it every 15,000 miles, others say when the onboard computer says you have 40-50% "oil life" remaining. Is there a correct answer ? Obviously I want to change the oil beofre it could be damaging to my engine but on the other hand, at the price of an oil change of synthetic oil ( around $70 ), I don't want to waste money changing it too often. PLEASE...I don't want just opinions, just facts :). THANKS

Answer 1

I own a 2002 C5 and have changed the oil when directed by the onboard diagnostic computer for the last 50,000 miles.

The GM engineers have designed the computer to monitor the engine. They are on the hook for warranty claims so I figure that they know what they are doing. The synthetics do last longer as well.

I let the computer tell me when to change my Oil.I believe that all C5 vettes use synthetic Mobile 1, 5W-30. I understand there are two primary considerations. 1) never use anything heavier than 5W-30 as this will rob power and potentially raise compression and damage internals. 2) Never, ever mix synthetics with petroluem iols....bad chemistry.

Hope this helps....just one mans opinion on letting the computer drive oil change schedules.

Answer 2

Bigspif:
It is refreshing to read your coherent post and request for factual information, something that is lacking in the maintenance and repair section.

I am not familiar with the Corvette on-board computer, but do know the Mercedes Benz (MB). I think your question can be partially answered using them.

A typical MB, such as the E320, has 8.1 quart engine oil capacity. MB has their own specification for pure synthetic oil. When the oil change is done the computer is reset and change oil interval is displayed as 10K miles.

Each trip is then 'scored' by the computer (distance, number of starts, engine/ambient temperature, driving style, etc.). The computer increments up or down based on these various conditions. I have seen the oil change interval go down to 6K miles and up to 15K. The higher mileage would be obtained, say from long highway driving at moderate speed.

One significant point is that this computer is calibrated for synthetic oil. Normal oil would not hold up in the same way.

So one basic question: what oil type does the C-5 expect to have in the crankcase? For which oil type is the computer calibrated? I am guessing dinosaur oil, else wise the answer would be found in your owners manual, as it is for MB.

Apparently the by-products from syn oil aging are not (as) harmful. However, like any fluid, it will reach a saturation level from combustion and blow by. It can only carry so much sludge before replacement is required.

So do some more homework and see what you can find. Perhaps another poster will have more info.
Marc

Answer 3

Yes. Truly synthetic oil only needs to be changed around 15,000 miles. I still replace the filter with an additional quart of oil at least every 6 months, depending on how spirited she's driven. You can't go wrong with the 'smell' test. If the oil is black and smells like unburnt gasoline, it's time for a change no matter how many miles. The key is 'truly' synthetic. There are many quasi synthetics out there, which is only a percantage synthetic. Usually around 33 or 50 percent. And yes, a Corvette motor was built with a little more care than the other small blocks. ie, tighter tolerances.

Answer 4

Corvette 2001

Answer 5

I have an LS6 motor in a Cadillac and i depend on the Oil Life Monitor system , like the one in your car,to tell me when to change the oil. This is a sophisticated monitor that takes into consideration not only miles driven, but what kind of driving.. ie stop and go.. long distance... oil temp cycles etc.

Think about it. If the computer wasn't programmed for maximum engine life and it was keeping the oil in use too long... don't you think GM would be opening itself to all kinds of warranty claims?

More than you would ever want to know is here
http://neptune.spacebears.com/cars/stories/oil-life.html


addendum. I just noticed you have a 2001. I am not sure what the Oil Life Monitor does in that year of car,, But, for what its worth I have a 2002 Avalanche with an 8.1 liter and i use the Oil Life monitor in it to change the oil. 140K miles.. no problems and this engine is notorious for using oil.

Answer 6

2001 Corvette

Answer 7

Some say up to 7,000 miles.

Really finicky owners do it at 3,000

I always use Mobil 1 and change at 5,000 miles. I have 194,00 miles on a super clean 94 LT-1! No sludge, no problems.

It's more important to use a high quality iol filter. The cheap ones are NOT good at all.
Recently, I've been considering using Royal Purple, which is supposedly good for 7,000 miles.

Answer 8

Please for your car's sake do NOT wait till 15000 mile to change the oil, I change the oil in my cars every three to four thousand miles, you can wait till 5000, but I'd rather be safe than sorry, espescially with a Corvette.

Answer 9

company or fleet trucks oil is changed every 5k miles , instead of 2500 miles, synthetic oil should last twice as long deepening on city or highway . look at the dip stick after 2500 ,5k and 7500 miles, you can get 10k miles of use from synthetic oil.

Answer 10

a high quality oil filter will keep the oil cleaner longer. synthetic is supposed to last longer than dino oil, but it's too pricey for me. i just use dino oil and change it at 3k, no more than 3500 on my cars.