Hi Schwa,

I've owned two colts, a 1987, and a 1992. The 1987 gave it up after one too many MVA's; and I, despite *really* liking to drive the 1992, traded it in for a Honda civic when it refused to stop rattling at high altitude, and I found out that the brakes were not the best in that car line. The things newborn children cause us to do ..

I think I put regular (87ish) octane fuel in both cars, but was always a bit nonplussed by the mediocre FE. Mitsubishi just has not kept up technologically, and of course the later cover-up scandals and rebadging of hyundai aka Mitsu precis really hurt their reputation. Irrevocably for me, but I tend to hold grudges.

 

I've had a few different Colts, and they've been pretty good, altho since they are all old used cars they all have their issues at times. What I've found is that I can retard the spark timing and get away with using 87 octane, but that causes incomplete burns and bad power output and eventually my catalytic converter will fail, and then it won't pass Air Care Inspections. When properly tuned and with high octane gas the 1.5L engine puts out quite a lot of power for the car weight, and is even good on hills. Unfortunately all the Colts I've had were carburrated so there was no knock sensors and automatic timing retardation, those adjustments were manual, altho pretty easy with the distributor at the top of the engine. You'll get a lot of pinging and knocking if you just use 87 without retarding the timing, and that's about the worst thing you can do to an engine on a regular basis.

The additives in higher octane gas are there to ensure a more complete burn, since the burn is slower there's more chance of some unburned portion being left over, and the additives are included to help completely burn the remaining hydrocarbons in the catalytic process. They advertise them like it's good for your car and whatnot, but that's really just marketing at work trying to get people to buy the more expensive fuels. Regular gas doesn't need as much of the additives because it burns faster and more completely, they probably still put some amount of similar additives in, but not nearly as much because it burns cleaner on it's own.

 

Since I purchased the vehicle, I used 87 octane, until recently, I tried 89 and noticed an increase in MPG it went from 48 to 52.6, based on calculations of how much fuel was purchased, the Prius instrumentation averages seem to be alway 2 points lower.

 

Toyota strongly advises against using any octane rating over 87... anything higher can cause starting problems.

I personally haven't seen anyone yet who's gotten higher MPGs with higher octane ratings. You sure you haven't hanged driving habits or taken a really long trip and gotten the system warmed up and in prime operating mode?

There really should be no correlation. Some people have seen significant drops in MPG with higher octane ratings.

I suggest sticking with 87 to keep your car healthy.

 

Hmm my manual says on page 204:
OCTANE RATING
Select unleaded gasoline with an Octane Rating of 87 (Research Octane 91) or higher. Where did you get your warning from?

 

Howard: from the Toyota hybrid tech training manual

 

hey guys sorry to bring this up again for those who live in bc you guys ever tried husky/mohawk gas? They have that promotion of "midgrade fuel for the price of regular" and their lowest grade starts at octane 90! accross the street is chevron with octane 87 for the same price! The secret is they use 30 percent ethanol into the fuel which claims can reduce emissions and is cleaner burning. I've been running it on my civic for 5 tanks straight and I do notice a slight decrease in mileage but nothing too noticeable if you didn't pay attention. But hey I do notice a decrease in tailpipe (espically in the cold) and maybe the cleaner fuel is better for my engine... even though its meant for octane 87.

Thoughts?

also mohawk/husky claim their fuel is "mother nature's" and we are reducing emissions everytime you pump their fuel instead of octane 87. Marketing or fact?

 

It's a fact that ethanol blends burn cleaner, and can reduce CO2 emissions (unless the **** ethanol plant is fueled with coal) and I use it (Husky/Mohawk) in my Colt that requires at least 92 octane to avoid pinging/knocking. A tank of 90 octane went into the Prius once and fuel consumption went up, although other factors may have played a role as well, but the Prius doesn't generally take advantage of higher octane gas, although it can take advantage of E85 for increased power.

I say go for it since most cars will take advantage of the ethanol octane boost by advancing the timing for increased performance, besides being better for the environment and supporting the ethanol producers and farmers. Husky is building some new ethanol plants, so maybe they will be able to offer E85 at some point too! That would rock.

 

i never knew 01 priuses can take advantage of E85 fuel.

 

Not officially of course! but it was tested at a lab, and put on a dyno, it had more power and torque on E85 than using regular gasoline, but obviously the mileage dropped considerably.