Oil type change mpg?

[MurphBigHorn]

So I really don’t think this is possible but I figure I ask, and see what you all thought. Bought truck used with 12,500 mile on it. Truck showed 70% life on oil. Probably not reset. Well after haven to take it back. I ended up looking the truck over very well. Dealer had the truck certified. Said an oil change has to be part of the certification. But I didn’t trust them. Ended up doing an oil change. Went with penz ultra full synthetic oil. Also Took a sample of the oil and sent that off. Still waiting for results. I have never noticed this before with any vehicles I have owned. Always went full synthetic oil after 1k miles. So I Put 700 miles on the truck before the oil change. Best I could get was 16mpg. After oil change. Trucks getting 18mpg Now. All the same driving. Is that even possible? Could conventional oil to synthetic oil increase mpg?

 

[GKIII]

This is likely in the realm of "technically possible but extremely unlikely"...and that's only if the old oil was basically sludge. Simply going from conventional to synthetic isn't going to net noticeable mileage gains.

 

[rotts4u]

In short my belief is no. Also a difference of 2 mpg is not statistically significant. I am betting if you tracked your mileage for a year you would see differences of 1-2 mpg from tank to tank.

 

[Richard320]

Oil change alone, not likely. I have noticed that the ECO light comes on more often since I switched to full synthetic oil. But I haven't seen any improvement in fuel economy.

However.... if the tires were lower before and they got (over)inflated during service, that could help some. Supposedly mileage improves .2% for each psi underinflated. So check and be sure they didn;t pump your tires up to 50 psi when they should be 36 or whatever.

Did you switch gasoline brands? I used to buy no-name gas in my Jeep but got caught low once and filled up with Shell. MPGs improved 2 mpg that tank. I tried it again, and it held true. The difference in price was overcome by the improvement in economy. I've only used name brand gas since.