It took two years to figure this out...

At the start of summer two years ago I switched from, **5W-30**, Mobil-1, full synthetic, to **10W-30** Mobil-1, full synthetic. The engine had been getting about 2000 miles or more per quart till the change. At that point the oil consumption rose to about 800 miles per quart.

I continued to use the 10W-30 weight for two oil changes with the same high oil usage.

Okay, at this point I'm panicking and thinking I have one of the dreaded "oil burners". I took it in to the dealer for an oil consumption test. They changed the oil and filled it with the **5W-30** I had supplied. At 3500-miles I take the car in to be checked and it still hasn't used a full quart. The techs at the dealership looked at me like I was nuts when I told them how many miles it had been getting per quart. I continued to get about 4000 miles per quart (3000 miles on ¾-quart at my normal 3000-mile oil change) while using the 5W-30 weight oil.

Well the next year the hot part of summer rolls around again and I switch back to the **10W-30** weight that I use in all my vehicles.

Rats... Oil consumption was back! I still hadn't realized it was the different weight oil that was causing the problem. Once again the problem went away the next 5W-30 oil change.

Every time I change to 10W-30 it uses oil. Every time I use 5W-30 it doesn’t. Has anyone else noticed higher oil consumption when going to the heavier weight 10W-30 Mobil-1?

Yes, I know it’s not supposed to work that way, but it does on my car.

 

Now this is interesting. I'm still on the 5w-30 for my 03 ZO6 and it doesn't use any. Haven't gone to 10w-30 but was thinking about it. Maybe not anymore!

I use Mobile 1 10W-30 on two Japanese cars that are driven hard and neither uses any oil.

I, for one, have never heard anything like you've experienced. Might be an interesting thread. I can't figure out why the 10W would go thru your engine any faster. :steering:

 

Very strange, I use 10 - 30 Mobile 1 year round here in Pa. At 26,000 mi in my 98 no oil use at all. If thats happening in your car, then just use the lighter oil, all engines must be a little different.......... :chevy

 

Any chance you are just driving more aggressively (because roads are dry etc) when you have the other oil in?

I know my oil consumption is WAY up when I drive hard, race or dyno and is about normal when it rains : ) My car goes in tomorrow for new rings.

If you want to test it put the 10/30 in and do some dyno pulls and otherwise drive aggressively.

 

Many times the consumption of oil has little to do with the weight of the oil, but has to do with the Flash Point of the oil. Look up the data for M1 and see if the 10W30 has a lower flash point than the 5W30!