First oil change, mpg jumped ???

[Mudgen]

Had my first oil change yesterday, free at the dealer. They put in Mobil 5W-30. My gas mileage has jumped from 21.5-21.8 to about 25 on my daily commute. Do they use much heavier break-in oil?

[gwoods]

I don't know that .3 mpg is really a 'jump' I would expect the car to be faster and get better gas mileage after the first couple thousand miles when all the moving parts wear in. Do you know if they used an additive when they did the change? I run Lucas Oil Stabalizer in my G. The dealership I go to used to use a similar additive.

[Mudgen]

I don't know that .3 mpg is really a 'jump' I would expect the car to be faster and get better gas mileage after the first couple thousand miles when all the moving parts wear in. Do you know if they used an additive when they did the change? I run Lucas Oil Stabalizer in my G. The dealership I go to used to use a similar additive.

According to my calculator, 25-21.8=3.2. But I'm running Linux.

Yes, I expect the mpg to improve gradually out to about 10K. But 3+ mpg at once was a bit startling. Don't know if they used an additive, but there's not one listed on the ticket detail.

[joe603]

When I read it fast I thought the same as Gwoods...lol

That is a pretty big jump. I'd see if it stabilizes over time. My G37 will get 27-28 on the highway and I'm using Royal Purple.

[Mudgen]

Ah. Now I see what you're seeing. Sorry for confusing things by posting a range for "old" mpg and a discrete value for "new".

Yeah, I'll see what happens over the next tank. The 25mpg was over 100mi of my typical mixed driving, which is probably 10% town, 30% secondary highway (45-55mph), and 60% interstate (60-75mph).

[gwoods]

ya know reading comprehension has always been a weakness for me kindof like kryptonite is to Superman.

Ask them about the additive and consider adding it yourself if they don't run it. I'm at 100,589 miles and my G still feels like day 1

[Mudgen]

I've really never used oil additives. Used to use BG 44K fuel additive in my RX7s, and I Seafoam the geriatric F150 every once in a while, never paid much attention to oil other than checking/changing.