1995blacktattop

iTrader: (2)

the last time i got my oil changed the place didn't have 10w30 which i normally run because i had seen the check gauge light for the stupid oil pressure gauge a vew times last summer when it was really hot so i wanted a slightly thicker oil for hot idle to keep the pressure up. the last couple tanks since then have been almost totally highway but i have averaged 20 and 21mpg respectively. the last time i took highway trips like that with the 10w30 i was only averaging 18 or 19 mpg. i havent seen 20mpg in my car in YEARS (back in 2005 when i moved from FL to AZ i hit 23 or so because i had to put in regular in the middle of TX and ran with the cruise on and babied the car because of the octane) so my question is. all things being equal does running 5w30 give you 1-2mpg better fuel economy than 10w30? I found the cars original oil change receipt a few weeks ago and it was changed to 10w30 at its first oil change back in march of 1995.

96capricemgr

iTrader: (1)

At operating temp 10w-30 is not necessarily thicker, could actually be thinner depending on the exact oils you are comparing.

the first number is a cold number, the second the operating temp number and a RANGE at that. 0w-30 Castrol Syntec is actually a very thick 30weight oil and for awhile M1 10w-30 was thinner than their 5w-30.

10w-30 is fine by the manual above 0f. Also keep in mind north American oil recommendations are CAFE driven, not necessarily what is best for the engine.

That muddy the water enough?

Bottom line, if you like one oil over another, go ahead and use it, don't worry beyond that.

1995blacktattop

iTrader: (2)

thats probably why the original owner switched it to 10w30. it was in Hawaii when new and i bought it in FL. i don't know what i was running when i was in FL, probably 10w30. i know that last fall before putting the car away i switched to 10w30 to keep the oil pressure higher but now its back on 5w30. incidently i don't think the oil pressure at hot idle has been much different with either oil. this year it hasn't been as hot so i havent seen a CG light like i did last year. i attribute the CG light more to the oil sending unit that the trans shop broke in the fall of 2007 and that the one they replaced it with isn't as good since i myself replaced that one with one from autozone and the oil pressure immediatly dropped to 0 every time i let off the gas and came to a stop. i then returned that OSU and put the other one back in. i'm kind of getting off track in my own thread here but i guess i'm just curious as to how/why my gas mileage got better when the only thing i changed was the oil type. i'm pretty sure both oils were mobil 1 FWIW.

Badazz 97 TA

iTrader: (18)

more wind, hills, traffic, maybe you hit more red lights, maybe you were pressing the gas a little harder. Maybe the car idled longer then usual. There are too many factors to guess why your mpg's dropped only 1-2. I wouldnt worry about.


Or maybe just fill up your tires like Pres. Obama says to

1995blacktattop

iTrader: (2)

actually the mileage went up. i haven't seen 20+ mpg in a long time so i was wondering if going from the 10w30 to the 5w30 is what caused that.