2nd Gen Regular v Mid-Grade v Premium Fuel Experiment

Looks to me that your best overall mileage was with 89 octane. That's what I use, and I've averaged 20 mpg overall since I bought the truck.

 

because we're all secretly planning to get a prius as our second vehicle and want to justify the cost.

Yea, I typically run 89 as well.

 

I have run mid-grade since new also. Around here, though, octane is 86/88/90. Some altitude thing:

Short answer: You can get by with lower octane numbers at higher elevations.

Longer answer: In a gasoline engine the fuel/air mixture is compressed before being ignited by the spark plug. When you compress a gas it heats up. If this mixture heats up too much it will ignite before it's supposed to, something commonly referred to as knocking. The octane number is a measure of how well gasoline can resist knocking. At higher elevations the air is thinner, so it heats up less when you compress it. This means that the ability of the gas to not preignite is less important.

 

I'll try that when I go to Colorado next month.

 

Thanks for posting this info @ziggynagy

I'd be curious to see any testing that shows the difference in HP/Torque of a 2nd gen running 87 vs 91. Anybody see any charts or write ups on this? I'd consider running 91 on certain road trips when I'm loaded up heavy with my slide-in camper and gear going over the mountains.

 

Supercharged and turbo motors still need the higher octane right?

 

Have made several trips from Memphis to Colorado over the years, never had a problem with the lower octane fuel while there. One thing I recommend is fill up with lower elevation fuel (ie 87 or higher) as soon as your return to lower altitude coming home, to reduce the chance of pinging from the lower octane/high elevation gas.

 

Yes and, most likely, cooler spark plugs.

 

Because when I filled up this morning there was an 80 cent difference between regular and premium. If the cost could be justified, I would do it regularly. As of now, I only use premium (non ethanol) when driving long distances, often towing my camper, in the mountains.

 

yep, higher cylinder pressures to create more torque/power make the fuel more volatile. the cooler plugs are a way to reduce the chance of preignition from the heat on the plug rather than the spark itself. i've been running 1 or 2 step colder plugs on my turbo cars for years. gapping them down tighter too can help too.

My buddy experiences pinging on 87 but not on 89 octane. ive only had mine for a week i havent noticed it yet. the way the trannys like to keep you in overdrive and lug itself around at low rpm doesnt help motors are quite susceptible to knock at low rpm. for mpg id say you want to run the lowest octane without pinging. once the motor really starts to knock the sensor pulls timing reducing power and efficiency. when towing or loaded down its probably better to run high octane to keep the motor off the knock sensor and running as much timing as possible for power/tq output. remember that torque output dictates fuel consumption. if you are looking to make some power/tq, its going to use up some fuel...