Hello, first post here. We have a brand new 2013 Prius Two, just took it out for it's first drive yesterday, Ogden to Provo and up Provo Canyon to Heber City and home via Weber Canyon. Hills, mountains, straightaways and twisty roads and the car seemed powerful enough to pass anywhere and smooth with less road noise than our Jetta TDI. (more later) After our drive we ended up at Costco so decided to fill up. When I pulled up to the pump they had only 85 and 89 octane, the 89 was twenty cents more a gallon but I know the owners manual says 87 and didn't dare go with the 85. Is 85 close enough? I know going higher than 87 octane provides no benefit and perhaps less energy.
As stated by Retired4999, 85 octane is common in higher altitudes (equivalent to 87 octane at sea level)
I have used 85 Octane everywhere it has been available (MT, WY, CO, UT for my travels, in Prius and four previous non-hybrids) for over thirty years, and have never had a problem with it. The two oldest cars had enough carbon buildup to have ping problems on 87 octane at elevations below about 1000 feet, but had no problems with 85 at the 5000+ elevations where I found it available. It seemed that 85 was traditionally not sold within normal fuel tank range of lower elevations where it could be a problem. But with the longer fuel range of modern cars, it is something to think about when traveling far downhill immediately have fueling up.
My understanding is that 85 octane at 4500 feet is like 87 octane at sea level. If you get too close to sea level on that same tank of gas, there would be issues.
I'm curious if you noted this, but do you know what kind of gas mileage you would have gotten with the TDI and with the Prius on that same trip?
"I'm curious if you noted this, but do you know what kind of gas mileage you would have gotten with the TDI and with the Prius on that same trip?" Yes, we're on our 2nd TDI, both Jetta wagons, 2001 and 2009. Our first was an automatic, our current one is a six speed manual. Both would have averaged about 37mpg on that trip. The Prius got 48mpg. The TDI is a great car, and with the manual is very sporty. We're keeping our 2009 in the family, selling it to our kids. We just got tired of the $0.80-0.90 to a dollar difference in the price of fuel. We're keeping our 2004 Dodge Cummins though, 22mpg and not a single issue so far.
I don't own a Prius, but my TSX is designed for 91 octane and the manual states it can run on as low as 87. That said, I filled up with 85 when in MT. Highway cruising is easy and doesn't require a high octane. Elevation further reduces the need for higher octanes. At about half a tank left on the 85 octane fuel, I came upon Fourth of July pass where I would sustain a long hill climb, and eventually end up at a low elevation in Portland. Hill climbs, acceleration, lower elevation all require higher octane. Basically, anytime more air is being drawn into the engine due to higher air density or pressing the accelerator harder. I filled up with premium fuel at the bottom of the pass so that I could bring up my octane for the hill climb and eventual decent to 100ft elevation. To answer your question, I would fill up with 85 as long as I was planning to stay at high elevation for the duration of the fuel in the tank. Another trick I sometimes do is to pump about 50% of my fill with premium and then fill the rest with regular. This is often cheaper than using mid-grade, which in Oregon/Washington is 60% regular and 40% premium. The very frugal will also note that pumping regular fuel after the premium will ensure all of the premium you paid for is pumped out of the hose.
He said that because Costco isn't a top tier fuel retailer.(BP is likely the supplier for Costco) That said, the only thing special about top tier fuel is extra detergents that are used to keep the fuel system clean. The gov't sets the minimum level of detergents, and top tier fuels use more. I don't see a need for top tier because I've never had an issue with my fuel system in the hundreds of thousands of miles I've traveled on Arco gas. You can also purchase detergents and add them to your fuel tank periodically if you're concerned about not having adequate detergent in the fuel.
The refineries sell different versions of their gas, some with a certain level of detergents, some with a lower level. Not all gas from the same refinery will be rated top tier, which includes the gas they sell to third party retailers. In other words, they keep the good stuff for their own stations.
That likely varies from market to market. In most areas, a very few refineries supply nearly all the many brands.
