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Old 02-13-2022, 05:19 PM   #51 (permalink)
Isaac Zachary
High Altitude Hybrid
Join Date: Dec 2020
Location: Gunnison, CO
Posts: 1,557

Avalon - '13 Toyota Avalon HV
90 day: 40.45 mpg (US)

Prius - '06 Toyota Prius
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I thought I'd mention a few more things about octane and compression ratios and fuel consuption.

Take the Mazda Skyactive-X SPCCI engine for an example. It has a compression ratio of 16.3:1 and yet runs better on 80 R+M/2 octane than anything higher, including 87 which is regular in most states. 91, or premium, is actually worse for it than regular. Of course it works on a different principle than traditional spark ignition engine, but the point is an engine can be designed to not only get good fuel mileage at high compression ratios and low octane, but it can actually be designed to need low octane.

A hybrid that needs premium fuel is still a bad design in my opinion.

Say two people buy 2022 Corollas. One buys a non-hybrid that costs $20,175, and a the other buys a hybrid Corolla that costs $23,750 (MSRP for both). According to the EPA, the hybrid gets a whopping 52mpg average but the non-hybrid only 33. Say the non-hybrid owner pays the current average for regular fuel at $3.48, but the hybrid owner pays $4.08 per gallon because he uses premium, which on average is 60 cents more than regular nationwide. Assuming all other costs are exactly the same, the hybrd owner will finally have spent the same amount of money on the car when both cars reach 133,000 miles (214,000km) each. Which, if they drive 12,000 miles per year, will take over 10 years for the hybrid owner to break even. Then after that the hybrid driver can actually start saving because of his decision, until he needs to replace the HV battery or special brake actuator or something similar.

But say both spent their money on regular fuel. Then in 93,000 miles (150,000km), less than 8 years, the hybrid owner will finally break even and can start saving.

And the Corolla is kind of an extreme example IMO. The hybrid version could have been more, as much as 20% more, not 17.7% more like in this case. And hybrids don't always get 57% better fuel mileage than their counterparts. If it only got 17% more but needed premium fuel, then even if the cars cost the same to purchase you would never save money if you paid for national average fuel prices. 30% better fuel mileage would mean you would have to drive nearly 200,000 miles just to break even if you use premium in the hybrid.

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