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MetroMPG 01-14-2019 11:40 AM

Question about Subaru Forester: better to accelerate at 1500-2000 RPM or 2500-3000 RPM?
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Iíve been using a ScanGauge for years, when the II came out, they let me buy the circuit board for $15 and install it myself.

Every time I fill up, I register the fuel amount. The ScanGauge II usually anticipates the fill-up to within 1/10 litre ó roughly half a cup.

I have a 2018 Subaru Forester and Iíve been accelerating at 15-20 percent throttle, usually 1,500-2,000 RPM.

Iím wondering if 25-30 percent throttle or 2,500-3,000 RPM would be more efficient.

MetroMPG 01-14-2019 11:45 AM

I assume your car has the CVT. In that case, I'd say opt for the lowest RPM you can get away with.

Modern CVT's will load up the engine while keep RPM remarkably low -- if you keep your foot out of it -- which is better for overall economy.

And if the car has a "manual" shift mode (buttons or a different shift gate), consider using it to request even earlier "upshifts" than the default programming gives. That will save even more fuel, especially if you can get to "top gear" sooner and at a lower cruising speed than the default programming would otherwise do.

See: "Short-shifting" a Jeep Patriot & Audi A4 CVT (forcing early "upshift") saves gas

Having said all this, how you use the BRAKE pedal (or don't use it) has a bigger impact on your overall economy than what you do with the gas pedal (other than on the highway, of course). Food for thought.

redpoint5 01-14-2019 12:35 PM

I'd say acceleration technique minimally affects fuel economy, but avoiding brakes and excessive speed is everything. My strategy is to target 80% load. I tend to shift a bit early if there's nobody behind me that would be slowed down, otherwise I just fit with the flow of traffic. Nobody's going to be impressed with the half-percent fuel economy improvement if they miss a green light because someone wasn't accelerating fast enough.

Joggernot 01-15-2019 08:01 AM

I have a Honda CRV with a CVT. I "assumed" the engine sweet spot was ~2000 rpm. I accelerate at 2000 rpm all the way up to 55 mph. Don't know if this is good or bad because there are two drivers in the family. Lead foot and me.

MetroMPG 01-15-2019 08:50 AM

Does the car have an ECO light?

Joggernot 01-15-2019 09:30 AM


Originally Posted by MetroMPG (Post 588775)
Does the car have an ECO light?

Yes, mine has an ECO light and I do use it.

MetroMPG 01-15-2019 10:41 AM

I wonder if the Forester does.

Do you find it's hard or easy to keep the light on while accelerating?

serialk11r 01-15-2019 11:47 PM

I mean there is quite a difference in BSFC between 1500rpm and 2500rpm on some cars, but I think with a CVT it's much less of a concern. When you drive stick, it's difficult to keep the load low enough at lower rpm to avoid enrichment and more importantly spark retard. Normally at 1500rpm the peak efficiency is something like -10% of peak overall, but you can easily make that drop much lower if your foot isn't very precise.

A CVT just bumps the revs up if you put your foot too far down and drops them if you are pressing too lightly.

On the FB25 and FA20DIT engines, compared to the FA20 you have a much lower compression ratio and TGVs, so I expect 1500rpm to have pretty good efficiency anyhow.

Joggernot 01-16-2019 08:45 AM


Originally Posted by MetroMPG (Post 588779)
I wonder if the Forester does.

Do you find it's hard or easy to keep the light on while accelerating?

I've never seen it go out. Turn on the ECO mode and it stays on. I've never looked at the dash when flooring it to pass, though. So I might have some testing to do later.

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