[earthworm]

1.Do gas additives do much more than make money for the company?
2.Will hotter plugs increase milage? I'm told that our modern computerized cars will sense the hotter spark & feed less gas to the engine for the same amount of power.
3.Do narrower tires increase milage? Or just make the ride & handling worse?
4.Are the 'high milage' oils worth a flip? I have 120K on my Silverado
& change oil & filter every 3-5,000 miles:will I gain anything?

[streeter69]

1. Some do and some just waste money.
2. Would not try it. Have seen shattered pistons cause of it.
3. They can increase fuel mileage due to lower rolling resistance.
4. Do not know, as I run synthetic in everything I own and all my friends vehicles.

[arrowdriver]

For octane boosters, check out SportCompactCar July 2005 issue page 136. Some interresting reading.

[Rob1035]

Originally posted by earthworm
change oil & filter every 3-5,000 miles:will I gain anything?

Sounds like you are pretty good about it already, I doubt you would get much benefit from changing to a more expensive fancy oil.

[vart]

...Unless he switches to Mobil 1 synthetic. It will reduce friction and you won't have to change your oil so often.

But, at 120k miles, I have personally seen Mobil 1 cause older engines to start leaking oil.