Cadillac STS Forum - 2005 through 2012 Discussion, STS N* v8 MPG in Past Cadillac Vehicle Discussion; Why would you even remotely consider dumping snake oil into your engine ?? ("oil cleaner" ? ? ? ?)
Automobile(s): 2002.5 F55 STS/65500mi, 2004 Ford F150 SuperCab4x4
MD Eastern Shore - Kent Island
Re: STS N* v8 MPG
Why would you even remotely consider dumping snake oil into your engine ?? ("oil cleaner" ? ? ? ?)
Open the oil fill cap and look in there with a strong flashlight. See anything that would make you want to dump in some extra goop that costs money and therefore drives up the cost of mileage - just as non-essential gasoline additives do. What does your (GM) owner's manual say about using additives ?
Engine oils, straight out of the bottle, already have everything needed to keep your engine clean and happy. Let others buy the junk that puts stickers on the sides of Dale Earnhardt's car.
When I was younger I had a 97 Altima and I bought a can of some oil additive. I happened to be taking my car in for an oil change so I gave the mechanic the can and asked him to add it in and he basically told me I was wasting my time. The stuff doesn't do anything. Ever since then I've been convinced that stuff is all a scam.
If you put in more than 17, you may be getting cheated by the gas station. My 2006 manual says 17.4 and my 2007 manual says 17.5. I've run it low, but don't remember ever putting in more than 17 gallons. (But I don't 'top off'!)
My 75% highway/25% city commute, which is ultra-predictable Fort Worth traffic, I'm deep into the throttle a couple of times per tank, 87 octane from Costco, same pump, same station every single time, and I get about 20.5-20.6, depending. On light timing and A/C use.
I track all my MPG, by hand, for all vehicles (save for my wife's current one), since my first 72cc Honda scooter back in 1984, and I can say you should be getting much better MPG.
I have the 3.23 rear, on Continental Extreme DWS tires, 38 PSI front, 31 PSI rear. Typical highway speeds are 60-65 MPH, gentle acceleration, backing off early for traffic/lights (I used to drive a tour bus for a living, you get very good at being gentle so as not to have any members of a bachelorette party spill their drinks on either themselves...or you), just 'saving' the car/tires/fuel for fun times.
I've been down in the 17's, but not much above 21.0. I've not taken it on any road trips, though.
Recommended inflation pressures have so many variables, I don't consider pretty much any of them, save for weight carrying, useful.
Tires, how they're driven, temperature, ride quality, handling expectations, wear expectations, noise, etc.
I experiment with tire pressure until I find what **I** like, and which performs as I expect, taking my expectations into account.
I run 38 front, 31 rear because the last set, fronts were excessively worn on both inner and outer edges, decent amount of tread in the middle, yet alignment was fine, and rears wore excessively in the middle, though the PO ran the rears at about 36 PSI.