rnln

I used to have around 20-21 mpg all the time, same route, same time everyday. I used to use Castro 20-50. Recently, I changed to Vavoline 20-50 and get around 26-27 mpg. At first, I thought I made a mistaken but this is the third tank and I got the same figure, 26-27 mpg.
No, I have not replaced anything except engine oil change. Actually I replaced fan belt and AC belt lately but that after the new gas mileage figure changed.
Is this the oil manufacture makes the diff. or is it the temp changed does?

Jay H

Some more data may help us...

What year 911 do you have?

How long have you had this car and how long have you been driving this route that nets you 20-21 mpg?

Where do you live (climate)?

Jay
90 964, 84 3.2

rnln

87 911 wide body conversion done prior. I have the car for proximately 1/2 year or so. Since first day, I've been getting around 20-21 mostly freeway, same route, same times, same same driving spirit untill 2 weeks ago. I couldn't find any Castro so I temp use Vavoline (same grade). Between that time now, I also replace fan/AC belts and leave it not as tight as before. Now I am getting between 25-26 mpg. Well, it's good, but strange. The only explanation now is.. I calculated it wrong

theiceman

I have never done any real calculations but i get about 520km to a tank ( 78 )

NeufCentOnze

I get 19-20 mpg on my 86 cab for "normal" open-road driving conditions, using Mobil1 20W50.
If a different oil brand really lowers consumption by that much then it is well worse knowing and I guess the increased engine efficiency must mean less wear??? Still it sounds unlikely given the same oil basic properties...

Cheers
Chris

rnln

what a affraid is more mpg = more wear.

Edward

Hmmm, that's a pretty significant difference, rnln. I'd doubt that only a diff in off-the-shelf oils would result in such dramatic differences. See what happens over the next few tankfuls and post back.

Edward

dugsud

I use Vavoline 20-50 and get around 26-27 mpg too! I've never used any other
oil though.

ron mcatee

Same with me. Valvoline 20w50 VR1 Racing oil.....26-27 mpg for past 7 years it's been consistent.

rnln

umm.. 4 people have the same comment with Vavoline oil. You guys make me really wonder. I really do think same oil grade from diff. manufactures don't make diff. The explanation to myself is that the traffic change but I didn't really notice it.
Yeah. Let me re-calculate again after several tanks of gas and another oil change, and will post result. I feel strange and curious.

theiceman

Guys rnln said something else that may be relevant. He changed his belts and did npt put them on as tight, If his belts were on way too tight would the engine not have to work a lot harder to turn them ? just a thought ...

wholberg

I have a 87 wide body Targa and I get 24 mpg at 70 mpg, and 26-29 at 55-60 mph. 20-21 mpg seems really low for a car in a good state of tune. I use Mobil 1.

theiceman

I get 21.8 MPG , it idles great , pulls strong , and never even a hint of a miss or backfire. That being said I have a 78 with no oxygen sensor or engine " electronics" to control fuel input. ie tps etc. MAybe I will loose my fan belt :-)

Norske

With Hioway driving, I always got 25 to 28 MPG with my 88. I think 21 is quite low unless you are in heavy traffic, stop and go. These cars get great mileage even going 80MPH+. If you are getting less than 25, you must be not in 5th most of the time.

theiceman

oh well , gas is cheap :-)