Synthetic oil and fuel milage?

[Tom S.]

What is the opiion on using synthetic's for improving fuel mileage? I bought my wife a 07 Impala with the big v-6, it is a 3.9 litre. It does not come close to the 29 mpg advertised for the road. It is not bad around town but on road trip's it is a gas hog.We had a 03 Cadillac with the 4.6 that did much better on the road.I thought maybe I could improve mileage by changing to synthetic? Duke what do you say? Tom

[mike cobine]

Re: Synthetic oil and fuel milage?

A friend noted better mileage with synthetic oil (Mobil 1) but it was only like 2 mpg more at most. And with the variables in doing gas mileage checks for most people, you can't really be sure it was the oil.

If your mileage is drastically off, and you have a couple thousand miles on it, I'd be back talking to the dealer.

[Clem Z.]

we have 04 impala with the 3.8 V-6 and

it get 29/30 MPG on trips ans 20/22 around town

[Michael W.]

Re: Synthetic oil and fuel milage?

All car manufacturers invest millions of dollars in R&D programs in order to produce cars that get the best possible fuel mileage, both for marketing purposes and to comply with government regulations.

If it were true that synthetics gave better fuel mileage, why isn't it 'factory fill' on all cars? The difference in cost between dino oil and synthetic (at OEM bulk purchase rates) would be just a couple of dollars per car.

GM could discontinue the expensive high tech programs that yield only a few points of improvement and save all that money to pass on the shareholders. Even F*rd might become profitable again!

There again maybe it's just more marketing BS- remember, we have wouldn't 'snake oil' without oil.

Hmm............

[Tom S.]

Re: Synthetic oil and fuel milage?

We get 20-22 around town and 24-24.5 on the road. Nowhere near the 29 adv. It has the fuel management system like the SS HAS.I have talked to several people that have those and the milage is not good on those either.Maybe after it get's some miles it will improve. The computer milage lies also. You can't beat the old pencil and paper method. thank's for the opinion's. Tom

[Duke W.]

Re: Synthetic oil and fuel milage?

The current EPA highway mileage number is based on a test cycle that averages 48 MPH, so in steady 70-80 MPH cruising, most cars will not achieve the EPA highway number.

When it was developed over 30 years ago, the national maximum speed limit was 55 MPH.

Within the near future a new test procedure will be phased in that includes higher speeds, faster acceleration, and use of the air conditioner, and it should yield more realistic numbers.

Be glad you don't own a Prius. The city/highway numbers are something like 60/50, but most owners in a mix of typical driving are getting low mid-forties.

Lower viscosity oil reduces internal engine friction, and the absolute viscosity of an oil is a function of SAE grade and temperature, so a 5W-20 will reduce internal friction compared to a 20W-50 at typical oil operating temperatures, regardless of the base, but the 5W-20 also has lower film strength, which means less reserve load capacity.

Contrary to popular myth, synthetic is NOT "more slippery" and a 0W-30 synthetic is going to have about the same viscosity as a 10W-30 mineral oil at typical 200 degree oil temperature.

The first number is the viscosity range at 32F and the second at 212F, so both are going to be about the same at normal operating temperature and there will be little if any measureable difference in internal friction or BSFC at typical passenger car engine loads and speeds.

Duke

[Joe L.]

Re: Synthetic oil and fuel milage?

Tom------

While I'm a big fan of synthetic motor oil, I don't think that you'll see any significant difference in fuel mileage between synthetic and conventional motor oils.

If you are using a conventional motor oil of the proper weight (5W-30 for your application) and of "fuel conserving" designation on the container (virtually all motor oils of major brands and 5W-30 viscosity will be so-designated), then that's about the best you can do from a fuel economy standpoint.

Also, from "EPA-rated" new car fuel economy ratings versus "real world" experience, you'll rarely find "commonality"---the EPA ratings are almost always higher than "real world".

[Harmon C.]

Should have bought a Corvette for good gas milage

I got 29mpg average form OH. to FL. and also to Texas for the Convention on my 04 with 20,000 miles. On cruise at 72-77 mph expressway driving.
Lyle

[Clem Z.]

Re: Synthetic oil and fuel milage?

the computer shows within .3 of a gallon on the fillups of what the pump shows. our computer MPG are very accurate. i never force feed the tank,when the pump shuts off i quit filling. i use mobil 1 change one a year change the filter every 4000 miles

[Clem Z.]

these new corvettes are great. my 97 with

the std rear gear would do 30 MPG on a trip the bowling green. all the rest have had the 3.15 rear gear and get 26/28 on the same trip. my friends new 505 HP ZO-6 get better milage than mine because he is turning about 400 less RPMs than me at 80 MPH

[Scott S.]

Re: Synthetic oil and fuel milage?

I have the same car, same engine. I used synthetic since 3000 miles and on a nice cruise of 150 miles or so, lucky to get 24 MPG. It's got 24K on it now & almpst a year old.

[Tom S.]

Re: Synthetic oil and fuel milage?

When we get ready to trde again I will seriously consider another Cadillac.They would not get right on the price this time or I would have had another.The power, ride, and overall comfort are worth something, not to mention the fuel milage was a lot better on the road.I am not happy with the milage on the Impala at all. Tom

[Jim T.]

Re: Synthetic oil and fuel milage?

Just completed a trip from Fort Worth to TN. Filled up at New Boston,TX and drove 375 miles home in my 96 LT4 using Mobil synthetic 5W30. Used crusie control on 70mph. Computer mileage indicated 30 mpg and the gas guage indicated above half tank of gas driving into the garage. Now have about 38,000 almost all highway miles on it. The new car sticker had 26 mpg for highway mileage. I really like this old Corvette.

[Jim T.]

Re: Synthetic oil and fuel milage?

Just completed a trip from Fort Worth to TN. Filled up at New Boston,TX and drove 375 miles home in my 96 LT4 using Mobil synthetic 5W30. Used crusie control on 70mph. Computer mileage indicated 30 mpg and the gas guage indicated above half tank of gas driving into the garage. Now have about 38,000 almost all highway miles on it. The new car sticker had 26 mpg for highway mileage. I really like this old Corvette.

[Clem Z.]

unless you drive in level country using the

cruise control get worse mileage because it do not anticipate the hills and ends up down shifting. i have tried this going to bowling green from pa. and it makes almost 2 MPG difference.