okay ANOTHER report

87 octane still

car runs better


I followed the advice of the guy in the other thread about turning off ECS and TCS this week. I went from 16.5 to 18.11 mpg !!!!!! ON the same routes to work this week - another definite improvement.

Remember - this same route in the BMW 328 was 19-20 mpg, in the Millennia S was 17-18 mpg. This mileage is in line with other cars from my experiences anyway considering these two cars were not as performance oriented. (BMW yes but its original 0-60 from BMW was 7.0 sec which they later changed to mid 6's)

 

I'm still running 89 and well, no sputtering or idle shake.

It really seems to make a difference I averaged 18mpg last tank driving like a mad man, ALL city.

 

Another tank another week 17.57 mpg based on miles driven from last fill up and amt of fuel.

 

I'm on my third tank of 87. I don't really notice much difference in power, but the shifter seems to vibrate less harshly. I'm not getting much in fuel economy as it's been about 15.7 mpg over the last couple of tanks for me.

 

I've been reading this thread with great interest. I will have to try some 87 fuel. However.....anyone have any information on the reason the octane rating (at the pump) for gas at 5000 feet is less than what you find at sea level? Here in Albuquerque 91 is the highest you will find. Does an engine require less octane at higher altitudes?

As for MPG. I now have about 800 miles on the car. The last in town driving fill up I got 17+. Now I either drive too easy or there is something to be said about driving at this altitude. I have seen as high as 19+ when I had some highway miles on that tank, but I don't think I have enough miles on the car to really said what I will end up at. I'll pass along my results with 87 fuel.

BTW I really do enjoy this car. I have never had a vehicle that handles as well as this one. I only wish we had some kind of track in New Mexico where I could push me and the car. That would be such fun!!!

 

Hmm, something I recently became aware of is that there are different features on the 8's that can effect MPG between models per se. The GT has this DSC/TCS system to disable via the button and others don't. Then there's the auto. (knew that one)

another note (said already) is the RPM econo driving - shift just below 3500 rpm. You really go thru the first 3 gears but supposedly only using one injector. This week my mileage consisted of mainly 10- 17 mile runs to work running the AC on 3 of the runs. Temp was in the mid 70's on 5 runs and in the 90's on 5 runs in humid air. 17.57 mpg with DSC/TSC off

 

reading the manual, it has list of recommended MPH shifiting points to get the best fuel mileage..

There are two tables, one for regular driving and one for touring I think. They vary VERY little. All points were between 3000-4000 RPM..

I actually tried to abide by that recommendation but I ended up getting UNDER 10mpg.. WTF...... I was so shocked. It seems the HARDER I try at saving gas, lately, the worse the mileage.. Shifting at low RPM's really made it worse..

Going back to my Normal driving (shifting at around 6000rpm with decent acceleration), I get 16-18MPG now.

Anyone experience the same???

 

Yea...the engine wants to be reved, that's for sure.

I'm getting better MPG partly because I'm through with the break-in miles, but also partly because I'm reving it higher, too I believe.

It seems that cranking up the revs really makes it perform more efficiently

At least that's my story....and I'm sticking to it.

 

Hmm, so maybe the car is meant to be shifted @ 5k to 6k rpm? Also have people encountered any pinging from the 87 octane? Wouldn't that hurt the engine?

 

I agree with the engine liking higher RPM. I also notice what others have mentioned - somewhere around 6300 or so, maybe 6500 a surge in power.

This week I drove slightly more aggressively - my mileage dropped from 18.11 to 17.6 mpg - not too big a difference. I now have 2400 miles.

 

I should top 4500 miles before I turn my car in. I'm at 3800 right now. I've consistently hit 17 MPG throughout the life of the car. Plus, the oil light always comes on at highway cruising speeds. I know there is a fix for this but have not bothered once I had decided to turn the car back in. I do not believe that any harm will come due to the oil light being on. I always check and make sure that I have enough oil.

 

This will be my last post in this thread.

This week I got gas and obtained 18 mpg. I drove the car much more aggressively than before and ran the AC 2 days (4 trips) on my route.

The only conclusions I can draw are that:

-the car runs fine on 87 octane

-normal driving - shifting at points from 3500 to 5200 or so seem to have little effect on overall MPG

-the car achieves its stated MPG estimate. Something my last two cars did not do.

I would like to thank those of you who posted your results. It was interesting and gave a "norm" per se for those of us wondering about the octane level, idle, soot and of course, MPG.

 

now the only question is, how is the performance on 87 octane? the problem is that we can't dyno the car, and I have seen articles in car magazines saying that the performance differences between octanes are not noticeable by the 'butt dyno'.

we need that 'speed racer' guy who got the 14.0 sec 1/4 time with his g-tech to try it again after 3 tanks or so of 87!

however, even these preliminary results are enough to make me want to run 87 octane except on autocross days.

 

Okay I said I was not going to post any more here but I finished a study over the past 3 weeks and thought some might like to know that driving habit definitely has an effect on gas mileage.

Some on here have said that you can drive the car any which way and it makes no difference. I found that it does.

About a month ago I was driving the car in town shifting quickly through the gears at about 3500 as my shift point. I consistently got 18 mpg.

So, the last 3 weeks I have driven like a banchee toning out and zoom-zooming all over - great fun BUT the gas mileage dropped to 16.2 - 16.5 mpg.

This goes along with the data on the air intake openings at certain RPM and the fuel injector activation at certain RPM. Obviously if you run one injector (under 3600 rpm) you will use less gas.


I know this contradicts my earlier post regarding rpm and effect but I now have more trials to base my new statement on.
So, on the days you feel like a conservative remember 3500 rpm and on those OTHER days, just have FUN.

 

this car is fun everyday

I cant help zooming everywhere

 

Yes it's FUN. I don't even figure my MPG anymore. If i'm paying a few bucks more to "drive it like you stole it," then it's well worth it. The chime needs to be heard daily or your not driving this car as it's meant to be driven!

 

you hit the nail on the head

 

I've had my car for almost a week and haven't noticed any idling problems or vibrations yet. I have been using 91 [R+M/2] gas and so far everything is ok. In the manual is says the use of 87 can and may reduce performance as well as engine damage and engine knocking. Has anyone here been using 87 octane and nothing else for their car?

 

It does not! :D

It says:

"You may use a regular unleaded fuel with Octane Rating from 87 to 90 (91 to 95 RON) but this will slightly reduce performance.

Fuel with a rating lower than 87 octane (91 RON) could cause the emission control system
to lose effectiveness. It could also cause engine knocking and serious engine damage. "

Do you see the difference between what the manual says and what you said?

regards,
rx8cited

 

My bad, you right. So has anyone done any research about which gas causes the idle shaking? Hard to determine myths and truths from the manual and the insight people are posting.

 

hi skagen ,

I forget to say that I've been using Shell 87 without any problems.

regards,
rx8cited

 

Sorry guys, excuse my noooooobness about gas. used to just always buy regular for my cool integra hehe so I don't know much about the difference between high end gas and regular. In the manual it says in the Anti-Knock index to use 91 (r+m/2) or (96 RON or above). But at the end of the paragraph it says

"Fuel with a rating lower than 87 octane (91 RON) could cause the emission control system to lose effectiveness. IT could also cause engine knocking and serious engine damage."

Is 91 (R+M/2) the same as 91 RON? I've been fueling up at 76 with the highest end gas. I thought that type of gas was 91 (R+m/2).

<-----------------------NOOB :P

 

No, here in the US gas pumps are labeled with the so-called "Pump Octane Number" (PON) which is the average of the Research Octane Number (RON) and the Motor Octane Number (MON). The MON is always lower than the RON. The manual for North American vehicles refers to the PON which is mathmatically (R+M)/2 where R is the RON and M is the MON.

Usually 91 Pump Octane is about the same as 95 or 96 Research Octane. The rest of the world still uses RON but The US changed to PON for some arcane reason back in the 1970s.

 

i just run 89 octane here in idaho, **** on that premium ****.

 

From what I have read most people that have been using 87 have not had knock. I have not been so lucky My 8's engine has knocked a few times using 87. Only the good stuff for my 8.