Milage and Downhill

[Donaldw]

I have an observation and a question.
Observation: Decided to fill up at Costco. They only have the low grade regular and premium. So got premium for 4.79/gal. That's about a dollar less than the medium grade I usually get at ordinary gas stations. What is surprising is the gas milage. I used to get 43-45 around town including some highway. At the moment I'm getting 50-51.
Question: Recent trip up to the mountains. Must have climbed above 8k feet. When going down a long (many miles) steep decline at about 50-55, doesn't require much foot on the gas, now and then the engine revs up and the charge gauge goes into green. I don't really understand this. I think it may have something to do with engine breaking.

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[BostonMaverick]

You drive a hybrid. The most basic explanation is that when you're coasting and braking, you're charging the battery. Downhill, gravity does most of the work, not your engine. The drivetrain will act more like an engine brake. The battery will be there to supplement your power needs to maintain slower speeds. MPG will be higher as a result. This has nothing to do with the grade of gas you fueled up with. The hybrid only requires 87. Premium fuel is generally a total waste of money for this engine.

 

[Gray Goose]

Regenerative braking is engaging on the downhill stretches.
https://www.sethwadleyfordofperry.com/blog/ford-regenerative-braking-technology/

 

[Donaldw]

Regenerative braking is engaging on the downhill stretches.
https://www.sethwadleyfordofperry.com/blog/ford-regenerative-braking-technology/

Thank you for the link. What I do not understand is why it would cause the engine to rev.

 

[awd]

What I do not understand is why it would cause the engine to rev.

someone recently posted some details about how the hybrid system works: https://www.mavericktruckclub.com/forum/threads/hybrid-power-meter-calibrated.49353/

it appears that if the battery is full (or also other conditions), that the electricity generated will be used to spin the engine (without fuel) in engine brake mode.

 

[MetalsGeek]

When the HV battery hits max charge, the PCU will engage the engine to provide "some" braking to reduce wear on your disc brake pads. It would not need to burn any fuel for this, but I suspect it needs to burn some to keep the cats hot. The Mav hybrid has a very small HV battery, so it doesn't take a very long hill to max out its charge.

 

[Raymundo76]

You drive a hybrid. The most basic explanation is that when you're coasting and braking, you're charging the battery. Downhill, gravity does most of the work, not your engine. The drivetrain will act more like an engine brake. The battery will be there to supplement your power needs to maintain slower speeds. MPG will be higher as a result. This has nothing to do with the grade of gas you fueled up with. The hybrid only requires 87. Premium fuel is generally a total waste of money for this engine.

FYI: Lets see what the Ford Manual says about Octane Rating; Quoting from my 2024 Maverick Manual as follows: "Your vehicle operates on regular unleaded gasoline with a minimum pump (R+M)/2 octane rating of 87. ....For best overall vehicle and engine performance, premium fuel with an octane rating of 91 or higher is recommended. The performance gained by using premium fuel is most noticeable in hot weather as well as other conditions, for example when towing a trailer." With AZ summers and/or driving steep grades ( such as Hwy 87 from Mesa to Forrest Lakes) 91 seems to be a good idea.

 

[BostonMaverick]

FYI: Lets see what the Ford Manual says about Octane Rating...

While it may not be clear, that recommendation is for the turbocharged engine. The hybrid uses an Atkinson cycle and that is different from the EcoBoost. I stand by the recommended 87 fuel type. Spend your money how you feel is best for your vehicle.

 

[Raymundo76]

While it may not be clear, that recommendation is for the turbocharged engine. The hybrid uses an Atkinson cycle and that very different from the EcoBoost. I stand by the recommended 87 fuel type. Spend your money how you feel is best for your vehicle.

The Manual does not say that the octane recommendations are only for non-hybrid engines. In the manual , Ford frequently goes out of their way to provide different info for both engines. If Ford wanted that to be the case, Ford would have so stated. While it is possible that this was an over site by Ford, with summer Temp often above 110, I do not want to take a chance. You see no risk; so as you say spend your money how you feel is best for your vehicle.

 

[BostonMaverick]

The Manual does not say that the octane recommendations are only for non-hybrid engines.

There are numerous pages across the Internet and many threads available on this forum that breakdown the hybrid fuel recommendations. Check out some of those threads as there is a lot of good information. There will be no harm running premium and if you feel it is beneficial, absolutely use it.

 

[MakinDoForNow]

Thank you for the link. What I do not understand is why it would cause the engine to rev.

When the HVBattery gets to 72% SOC or the recharge amps exceeds the amount the HVB needs to accept due to heat or other reasons the planetary gears will engage the engine to rev up without fuel 3500-4000 rpm acting as an air compressor. Then if more resistance is needed the hydraulic brakes can assist. Just have it in cruise and enjoy.

 

[Raymundo76]

There are numerous pages across the Internet and many threads available on this forum that breakdown the hybrid fuel recommendations. Check out some of those threads as there is a lot of good information. There will be no harm running premium and if you feel it is beneficial, absolutely use it.

Thanks for the conversation.

 

[Donaldw]

Regarding fuel economy, it is strikingly better with premium on our hybrid. What used to return 44-45 is now returning 49-51. And the costco premium is less expensive than the gas station middle grade. 17 mile trip today, mostly freeway modest speed: 53. Worth it.

I wonder if those who think no benefit have done their own experiment.

 

[BostonMaverick]

Regarding fuel economy, it is strikingly better with premium on our hybrid. What used to return 44-45 is now returning 49-51. And the costco premium is less expensive than the gas station middle grade. 17 mile trip today, mostly freeway modest speed: 53. Worth it.

I wonder if those who think no benefit have done their own experiment.

The only difference for me was when I was out of state and got a couple of tanks of ethanol free fuel. Locally all fuel is 10% ethanol. I ran premium exclusively in my EcoBoost and my first few fills on the hybrid were premium out of habit. I am now at 12k miles with 9500 miles using 87. My lifetime average is 51 mpg over the last 18 months.

 

[PSchiefelbein]

I use Costco 87 octane in my hybrid as the improvement in mileage doesn't justify the difference in cost. It is Top Tier for in Fargo, ND and I assume it is the same elsewhere. When a Costco is not available I look for a Top Tier station. I'm at 20k miles and have had no problems. My Mav does show a clear preference for warm weather, though.

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