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Old 02-13-2022, 05:43 PM   #52 (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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Originally Posted by Tahoe_Hybrid View Post
GM recommends you use premium fuel on the 6.0L or higher engines... they recommend it for a reason

btw this is an LS2 based engine. the 5.3 Flexfuel models also have profiles for higher octane fuels

if 91 oct did not work then why does AFM Hyper cycle the engine (between v8 and v4) when 87 octane is used?

when 91,93 oct you can actually accelerate in v4 with a mild up hill grade?
The reason GM recommends premium fuel in such engines is because such engines are not designed for economy. People don't buy vehicles with V8 6.0L engines to get good fuel economy. Such an engine is built for performance. They want to be able to haul around 10,000lb (sometimes more) trailers. they want to feel as though they got plenty of accelerator to spare. At this point fuel cost is the least of their worries. I personally wouldn't be bothered by needing to use premium fuel if I bought a Corvette, Silverado, Suburban, Tahoe or the like. I would buy one of those for what it can move or how fast it can move it, regardless of the fuel it needs.

This is like buying a Ferrari and asking if you can put cheap tires on it. That's not why you buy a Ferrari. Sorry, I hate to break it to you, but the Tahoe is not a vehicle you buy to get better fuel mileage in either. The hybrid system is a bit of a gimmick to sell cars. Hybrid systems in utilitarian vehicles are to give them more low-end torque. If you get slightly better fuel mileage then that's a small side benefit, nothing more.

In a car like my Prius things are completely different. The car feels like it has a boat anchor constantly attached. Towing a heavy trailer in the thing would be a nightmare. I can cram 5 people in it uncomfortably. But I didn't buy it as a people or cargo hauler or sports car or an off-road vehicle. It's a fuel sipper, that's what I bought it for. That's what people buy them for. And if I or any other Prius owner had to buy premium fuel, we'd be highly upset.

Here's a rule of thumb. If the car is built for fuel mileage, it will run fine on regular fuel. If it needs premium, it is not a fuel mileage vehicle. That is not it's purpose. You can try to get better fuel mileage in it. But you're going against your goal as soon as you put premium in there. Unless premium really is about the same price as regular.

As a suggestion, I'd recommend looking at water injection. If increasing octane benefits fuel mileage, then using something as cheap as water could lower your overall costs. Either that or a methane conversion as methane has an octane of something like 120, IIRC.
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