korlexus

According to some automobile experts that I've met,
most of Japanese cars(including lexus/infinit/acura) doesn't require to be filled with 91 octane even though it says on the gas tank. If you put anything below 91 octane on german cars, then you are screwed.
I guess they are right?!

greenchile

Ok, started the test today. Put regular (86) in it. We'll see how it goes over the next couple weeks to see if I need to put the premium (91) in it.

Rogarven

I will post here and the other thread. I filled up tonight with premium and we measured 22.2 MPG with mostly stop and go driving, very little freeway. I am very pleased!! I was also able to get prem. here for $3.29 per gal. so I think it is worth it, at least so far. :-) BTW, I calculated the old fashioned way, pencil and calculator. LOL

lgb0250

Since you are doing it the manual way it will be interesting to see how close it comes to what the computer says! Good luck

Rogarven

Really , the computer was very close to what it actually was! I was really impressed as this was better than the Accord V6 we just replaced.

igzy

I too do the manual calculation on every fill up (weekly) and compare it to the car's and they are pretty close...

christcorp

I must be lucky with my computer calculating. I still manually calculate mpg, but on the last 4 fill ups, all in town driving, manual calculations were around 20.28 average and the computer has said 20.3. Pretty close. I'll still do it manually, nut its nice to know its accurate.

igzy

My last fill up was 15.6 gallons after 476 miles and the car showed 30.5 mpg same that I worked out on paper

RainaES350

iTrader: (1)

Thanks for all the great information here guys, I will start using 87 octane!

christcorp

As has been said in this, and similar threads. Don't use 87 octane because "some" people here are using 87 octane. You use 87 octane because that is what "YOUR CAR" Likes. And the only way you'll know what your car likes best, is to run a couple tanks of each octane in your car and try and drive similarly. E.g. 2 tanks of 87.... then 2 tanks of 89..... then 2 tanks of 91. Determine how it drives, starts, pickup when flooring it to pass, gas mileage, etc... Your car will tell you what it likes and wants. Not a bunch of anonymous people on the internet. "Myself included". It's only going to cost you a couple of dollars difference to fill up the tank with different grades of gasoline and find out for yourself. Some cars work fine on 85 or 87. Some work better with 89. Some work better with 91. All I'm saying is: "Trust your car...... Not strangers you don't know on the internet". Your car will not lie to you.

garsarno

Amen to that. had a 2007 Hemi Grand Cherokee. Ran okay on 87, ran poorly on 93 and it loved 89

RainaES350

iTrader: (1)

Gotcha...will experiment!

fatbeaver1

I have a 2008 and use 89 octane. I too was amazed when I first got the car that it would get over 30 mpg on the highway going 70-74 mph. That is actual numbers calculated from filling up with a full tank then figuring how many gallons are left on the next fill up. I find the trip computer is off .5 to 1 mpg from my calcualtions.

MikePA

Guessing at gallons left in the tank is not used to compute mpg.

greenchile

I've had some strange results with my 86 vs 91 test so far. I've filled up 3 times now, with 86 octane, when the tank was down to about 1/4 full on the gauge. The 2nd fill up resulted in 24.5 mpg. The third fill up resulted in 25 mpg. being off by 1/2 to 1 mpg is pretty normal for me. What is strange is that I had used 91 octane exclusively since purchasing the car and had repeatedly gotten 22.9 mpg up until putting 86.

I would have expected my fuel economy to either stay the same or decrease, not increase by 1.5 -- 2 mpg. I have not run the fuel economy test long enough to feel good about the results though, just a little intrigued by what I'm seeing so far. I have not been able to detect any pre-ignition pinging using the lower octane. I have noticed that the throttle response is just barely slower than before the switch. I think it's perfectly reasonable that I may just be seeing normal variations in fuel economy based on where I had driven in the week prior, doing more or less city driving than commuting that week than in previous weeks. So I'm probably going to give the 86 octane a couple more fill ups to see where the numbers go and then switch back to 91 to see what numbers I get after the switch.

In case you're wondering about the low octane ratings of 86 and 91, those are the regular and premium ratings in my town, Albuquerque, which sits at 5,000 ft above sea level.