mpg and FP on one Subaru 2.5 engine

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As promised, for those of you interested.

I have a route that I take every couple of months that is lightly traveled and about 275 miles long. I am able to set the cruise control, and only turn it off when going through small towns, for a rest break, or the occasional passing of a slower vehicle. I set the cruise at 63 for most of the trip, with a 50 mile section where I set it at 73.

On most trips, I got 33-34 mpg. Get the same numbers on the return trip. Had GC 0-30 oil in crankcase. Changed to PP 5-30 in the crankcase. Got 36.2 mpg and 36.1 on the return. Began using FP, got 37.6 one way, 37.3 on the return. The only other thing that was different was the temperature...it was warm enough this trip that I used the AC. Oh, yeah, and I used the cheepo-gas instead of Shell or Exxon ever since I began using FP.

The last part of the trip is interstate, where I run around 80 mph, ac on the entire time. Mileage dropped to 30.5-31.5...this is slightly worse than the last couple of non-FP trips (31-32 mpg), BUT, the ac was on the entire time on this trip.

These results are probably within the range of noise, but, at the very least, the FP certainly isn't hurting the fuel efficiency. The one thing that is certain, is my idle is now smoother...it used to hiccough at least once when sitting at a stoplight.

Oh, car is rated at 22/29 EPA. Last city mpg I got was 31! Did a lot of coasting downhill and being especially alert for any opportunity for increased efficiency. And, my "city" is a small town...not a megatropolis.
 
Wow, that is great gas mileage on the 2.5 engine. Why not try 5W20 to see if you can get the mileage up a little bit more
smile.gif
What kind of Subaru is it?
 
Should have used the same gas (type/grade and even the same station) for the comparison.
 
My wife's Honda averages 38.5 on the highway at 75 MPH with the A/C on, regardless of the brand of gas.

I made a trip last year from Miami FL to Charlotte NC (1500 miles round trip) and got 41 MPG on the highway with FP60. Some people notice gains with FP60....others don't.
 
Do you guys think maybe the engine is just loosening up, and that is what is contributing to the increases in mpg over the past couple of months? It just has 17000 miles on it. Maybe the change in oil, use of FP, and warmer weather (in spite of more A/C useage) are just coincidental to a loosening engine. Do they really get THAT much looser? Just wondering...

Oh, BTW, it's definitely doing the "drop 1/4 inch on the dipstick when running 80 mph, but then stay right there" trick. I'm not refilling it back up anymore...it likes it at that slighty-less than full position. And, who am I to argue with it?
 
Dr. T, yep. Certainly isn't science I did there.

George, according to one poster in the UOA section, 5-20 seems to be getting good results in this engine. Under warranty for another 33,ooo miles, so, I'm not going to force the issue. My opinion is that it would do fine on the SM, GF-4 rated 5-20s. BTW, it's a Saabaroo...a Saab 9-2X...don't let that fool you though, it's an Imprezza wagon in better clothes.
 
that mileage is pretty nice - i drive an STi, and can only get about 21 mpg at my best, usually stays around 19-20 though... heh
 
Jealous of 20 mpg?
Heck I'm thrilled to getting 20 - 20.5 mpg in my
87 Volvo 745 Turbo Station wagon with a Cd of .39.
Last year when I wasn't using FP in the gas tank I was lucky to see 18.5 to 19 mpg.
 
ALS, do you think you may be getting better mpg with the FP? It seems like it might be so to me, but, I haven't eliminated enough variables to unequivocably make that statement. It CERTAINLY isn't hurting my mpg!

gnef, yep, seems all the turbo guys with the Subaru engines (2.0 or 2.5) say the same thing...even if they aren't driving it hard. My guess is the ECU simply isn't set up to get maximum economy, even with the boost "off". OR, these things get into the boost very easy. I don't know, I've never driven one. I've had lots of turbocharged cars, so, I knew not to even drive one of these with a turbo!
 
Titan there hasn't been a single change in the car except the FP60. I still run the same tire pressure, oil is M1 10W30, and my maintenance dose of Auto-RX. I'm a believer that it does work just by what I'm seeing. Although I have been using Exxon 89 exclusively since it is the cheapest gas around me.
 
ALS, based on what is happening in my two Subaru engines, I have no problem believing that FP60 increased efficiency. I just haven't done a good enough test to be able to scientifically prove it, so, I can't say it is fact.

I just put a dose of FP60 in my elderly father's 3.8 GM. I'll be curious to find out if his mpg changes. I told him it's just a cleaner, don't want him to think it will do anything to his mpg. We're alike in that we check every tankful we ever buy, so, I expect to hear from him if it's use coincides with anything unusual!
 
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