As I have mentioned in another thread, I am looking into purchasing my first Subaru. I have been reading about the 2014 Forester 2.5i CVT and once in a while people will strongly suggest using premium.
Is this necessary? Will I get horrible MPG or ruin my car if I use regular unleaded?
Here's Subaru's guidance on fuel requirements for the U.S. market 2014 Forester (ref 2014 OM page 7-3
The engine is designed to operate using unleaded gasoline with an octane rating of 87 AKI (90 RON) or higher
The engine is designed to operate at maximum performance using unleaded gasoline with an octane rating of 93 AKI (98 RON) or higher. If 93 AKI (98 RON) fuel is not readily available, unleaded gasoline with an octane rating of 91 AKI (95 RON) or higher may be used with no detriment to engine durability or driveability. However, you may notice a slight decrease in maximum engine performance while using 91 AKI (95 RON) fuel.
Regular unleaded gasoline with an octane rating of 87 AKI (90 RON) or higher may also be used. Using regular unleaded gasoline will not be detrimental to engine durability, nor will it affect your warranty coverage. However, depending on your driving habits and conditions, you may notice a decrease in maximum engine performance, fuel economy or slight engine vibration or knocking. If you experience any of these conditions while using a lower octane rated fuel, you may want to return to using 91 AKI (95 RON) octane rated fuel as soon as possible. Additionally, if your vehicle knocks heavily or persistently, or if you are driving with heavy loads such as when towing a trailer, the use of 91 AKI (95 RON) or higher grade unleaded gasoline is required.
I regularly experiment with this volatile issue
. For your area's general elevation, I suggest you try 87 AKI (low elevation "regular") in the colder months, and 89 AKI (low elevation "mid-grade") in the warmer months. If you see no improvement when using 89 AKI fuel, then just run 87 AKI year 'round. However, operating with a full load and/or towing a sort-of heavy trailer (using Subaru tow specs) may warrant 89 AKI fuel, especially in the summer.
"Premium" fuel (93 AKI at low elevation) in a 2011+ Forester FB25 non-turbo engine would be a waste, IMHO. And, other than urban legend, I've not seen any evidence that would suggest premium grade fuel would harm your engine in anyway.
My '12 Forester delivered its best overall fuel economy run (mileage + distance) last September: 479 miles on 15.37 U.S. gal. of Shell 89 AKI
from Erie, PA, to Guelph, ON, via Buffalo, NY, and then back through Buffalo to central PA. That was 31.2 mpg at a fairly low elevation (mostly under 1,000 ft).
Another good run was from eastern TN via I-26W, I-81N, and I-66E to northern VA in April, 2012: 416 miles on 12.99 gallons of a blend of 87- and 89 AKI fuel. That was 32 mpg.
We currently live is western NC at ~2,700 ft elevation. I've not seen any significant local fuel economy difference between using 87 AKI and 89 AKI fuels in the Forester. However, we experience an ~600 ft elevation gain over the last mile of road to our house, and the engine definitely pulls better on 89 AKI fuel. Specifically, there are two turns where I need to drop to first gear when using 87, but I can stay in second gear when using 89. It's an ignition timing thing...
And, a final comment regarding fuel octane (AKI) ratings and performance, and I love this one. Subaru of Australia specifies a fuel requirement of 90 RON (~86 AKI) for their new Forester with the FB engines
. However, this disclaimer is added:
@ All performance data measured using 95 RON as required by Australian Design Rule 81/02. Vehicles tested in accordance with ADR 81/02.
95 RON fuel is ~91 AKI in the U.S.
Jim / crewzer