1997 q45 engine oil usage and lower fuel economy

[Qproject]

on this link below, it states that Fuel economy may be lower after an oil change if the proper SAE grade (5W-30) is used. (1997-98)

http://auto.consumerguide.com/...ility/

so which oil grade do you guys reccomend ?

[qship96]

pretty sure they meant to say"if the proper oil grade is NOT used",as in if you used a thicker grade {10w-40,20w-50,etc} than the specified 5w- 30 weight oil

[Q45tech]

Many of the repair prices are wrong and understated some significantly.

For longevity 10w30 would be the minimum viscosity with 10w40 after 150k.

5w30 is speced to improve mileage not engine life.

[qship96]

qtech- would you use a 10w-30 over a 5w-30 in a cold weather state in winter{ -10 to +20 degrees f.} ?

[greenwar]

Hmm, so I should be using 10W-30 on my 110K motor? I live in MN, but vehicle hibernates in a climate controlled garage in winter.

[Q45tech]

I assume in the very coldest regions members use some type of oil/coolant heater element if they park outside and the temp gets below 20F frequently...............necessary no matter what viscosity you use to maximize life from abusive cold starts.

[Q451990]

Now this opens a whole new can of worms... at what point (if any) should I change our G35 over to 10W-30 from 5W-30? How about my truck with 125K? No oil consumption on either...

Heath

[Q45tech]

You always select viscosity by graphing the most extreme hot idle pressure under worst case brand new fresh oil and filter.............this corrects for differences in brands and molecular sizes of components in oil.

Oil pressure goes up as oil degrades and thichens from evaporation.