Subaru 2009 Forrester XT and Rotella T 5-40 questi

[gene_c]

I have been using PP 5-30 and Valvoline Synpower 5-30 in the car since new, the odometer reads 12,000. My highway fuel mileage typically is about 25-25.5 at 75 mph with the AC on with 5-30. Last change I switched to Rotella T 5-40, my highway mileage dropped to about 22.5 to 23. Is this pretty much the norm when switching to a 5-40 from 5-30? I'm pretty easy on the car, not much WOT stuff just some long grades on trips, I have been thinking of trying M1 0-30 green cap since I'm following the specified 3750 mi. changes. Any opinions? BTW, I'm in Southern California.

Gene

 

[Eddie]

good question to ask at www.naioc.com I thought that 5w30 was the factory recommended spec for the XT.

 

[oilyriser]

Does your owner's manual maintenance chart, by any chance, list DOT-6 fluid for the automatic transmission?

 

[bepperb]

That's a surprisingly large drop, so I'd guess there's something else going on. Two points I would make, one I would still run out this OCI, you're never going to save enough on gas to dump the oil. Two, going to a thinner oil and one with a low HTHS for it's grade (which th M1 0-30 has) will give you better FE, but usually not enough to notice and 10% is (in a lab/scientific setting) unheard of.

So, give it a tank or two. I could see .5 mpg. Not 2.5mpg.

 

[gene_c]

Originally Posted By: Eddie
good question to ask at www.naioc.com I thought that 5w30 was the factory recommended spec for the XT.


Actually the manual recommends up to 10-50 for desert driving.

Gene

 

[gene_c]

Originally Posted By: bepperb
That's a surprisingly large drop, so I'd guess there's something else going on. Two points I would make, one I would still run out this OCI, you're never going to save enough on gas to dump the oil. Two, going to a thinner oil and one with a low HTHS for it's grade (which th M1 0-30 has) will give you better FE, but usually not enough to notice and 10% is (in a lab/scientific setting) unheard of.

So, give it a tank or two. I could see .5 mpg. Not 2.5mpg.


It's probably more like 1.5 to 2 mpg.

 

[gene_c]

Originally Posted By: oilyriser
Does your owner's manual maintenance chart, by any chance, list DOT-6 fluid for the automatic transmission?


What is your point?

 

[KLowD9x]

Originally Posted By: gene_c
Originally Posted By: oilyriser
Does your owner's manual maintenance chart, by any chance, list DOT-6 fluid for the automatic transmission?


What is your point?


Ignore him. He is trying to be a [censored], but he doesn't pull it off well.

 

[deven]

Originally Posted By: Eddie
good question to ask at www.naioc.com I thought that 5w30 was the factory recommended spec for the XT.


Its www.nasioc.com you forgot the "s"

 

[oilyriser]

Canadian chart has an error in the rows, causing brake fluid to line up with the recommended fill for the transmission.

 

[gene_c]

Originally Posted By: oilyriser
Canadian chart has an error in the rows, causing brake fluid to line up with the recommended fill for the transmission.


No, I haven't noticed that one ). I understand now .

 

[oilyriser]

Just before the warranty runs out, get a case of DOT-6 fluid....

 

[bluesubie]

Similar mpg loss here, but I wouldn't switch to an oil geared primarly towards fuel economy such as AFE. Maybe part of my problem is that I've been less afraid to bury the accelerator since the 5W-40 is giving me a higher comfort level.

Does anyone think this could be due to lack of friction modifiers in RTS?

-Dennis

 

[sparkplug]

I never lost mpg's when I ran Rotella 15w40 in my Jeep, actually got the best (19) mpg's out of it.

 

[MrWideTires]

I have Rotella 5W40 in my Legacy... it's a good oil but IMO too thick, I'm gonna go with GC 0W30 next time.

 

[Gary Allan]

Originally Posted By: bluesubie

Does anyone think this could be due to lack of friction modifiers in RTS?

-Dennis


I've wondered the same thing. D1 appeared to have them (the other 5w-40).

Originally Posted By: sparkplug
I never lost mpg's when I ran Rotella 15w40 in my Jeep, actually got the best (19) mpg's out of it.


I can't say that I lost MPG with RTS ..but it was pathetic always anyway. I did see substantial gains with 0w-10, but that was wiped with aggressive treads on new tires. The engine felt like you were straining it above 3000 rpm (2.5). No such sensation with lighter stuff.

 

[gene_c]

I think I'm going back to Synpower 5-30. I got a steady 25.5 @75mph on an 1000 mile run with AC on. It's good stuff. I did the math on hiway MPG usng Rotella T on a 3750 change. It will cost an extra $39.13 using RT as compared to using Synpower 5-30. How is GC 0-30 on mileage, anyone know?

 

[bepperb]

GC is thicker than the M1 or the SynPower, and has a really high HTHS, 3.5 iirc, so it shouldn't do as well as either for fuel economy.

 

[chevrofreak]

The Rotella 5W-40 has a significantly higher 100C viscosity than the 5W-30 SynPower 5W-30 (about 40% higher). The 40C viscosity is also significantly higher. It's going to use more fuel.

 

[gene_c]

Originally Posted By: chevrofreak
The Rotella 5W-40 has a significantly higher 100C viscosity than the 5W-30 SynPower 5W-30 (about 40% higher). The 40C viscosity is also significantly higher. It's going to use more fuel.


I found that out in a hurry. I also found out that my car came alive after changing back to Synpower today. I never thought that there would be that much difference in MPG or power losses. The car now feels like the boost has been cranked up.