What grade gas you running in 3.0's
 

I have no problem paying for super if it gives me some improvement. My other car runs nothing but super.. but it also makes 475 HP. Given what happend to gas prices in the last month or so I decided to try plus grade (89 octane) in my 05 3.0 X5 and I see no difference. Anyone just running regular out there? I'm considering giving it a try but I'm not sure how much advance the computer can take out... I don't want it to ever ping. I'm sure the computer is retarding the spark with plus a bit but I really can't seem to notice. Maybe he difference between my X and my sports car is just too dramatic for me to notice a 5-10% drop in the X performance. Any SUV feels slow to me even the V8s..it's just physics.. but I did not buy it to be a fast car. So if it is safe I would rather just use regular.

We were doing the same - running 87 octane every other tank or half tank premium/ half tank regular. However, after explaining to my wife that premium is only $4 more per fillup, she said it wasn't worth the effort and has been using premium ever since.

But to add to your comment, we never really saw a difference in performance between regular and premium.

It's not just a performance thing, you're getting more detonation by using regular which could damage the engine because it's designed for lower detonation premium. It's also knocking the snot out of the knock sensor.

When you do the math, the difference between regular and premium over the course of a year is negligible compared to potential engine repairs that could result from the octane drop.

Guys, don't take this the wrong way, I know written words can't show the context or meaning of something said, but there is a reason BMW requires 91 or above. I am not a gearhead by any means, but it has something to do with the high compression engines or something ( someone correct me). And while your vehicles do have knock sensors, the extra $4-$5 dollars in the tank will feel like bus fare when you have to get your fuel injectors and whatever else low grade fuel causes. Just keep putting in the good stuff and dont worry!

Is there an echo in here? :)

1 other thing to add, running lower octane gas is going to eventually ruin the engine as you burn holes in the pistons and valves from all of the pinging. Remember, a knock sensor is reactive not proactive so it has to sense knock and then retard it, and keep retarding it.

In the long run, you'll save what? A few hundred $$$ a year, and a new engine costs what? $15k-$20k?

There's a reason that BMW says to use 91, and it's not because they own oil refineries :)

BMW tells also that the fuel consumption is better (car takes less gas) with higher graded gas. Your engine will also be a little bit more powerfull ;) So 4-5 $ is a good investment in your own pocket :D

Here's a X5World thread link with a plethora of posts/opins on the topic...
imo, I regularly run a tank of non-premo, during a long day's highway trip. Have never noticed a diff, performance or power or mpg-wise. Fwiw...
GL,md

http://www.xoutpost.com/showthread.ph...Gasoline+Grade

The real problem occure when low octane causes the car to pre-ignite. In this case the piston is still moving up when the charge ignites causing the force of the piston going up to slam into the shock wave of the gas ignition. This is horrible.. especially on a supercharged or turbocharged car. Burns rings, bends valves, etc.. lot of force at work. I run about 12 lb of boost in my other car and will only run supper coupled with a boost sensitive ignition retard. I've spend time on a dyno optimizing timing, fuel, and boost so I know under what condition I can run what octane. Sometimes I need race gas.

As the article states, a knock sensor will delay when the spark fires possibly reducing power and mileage. While that is true, I have not noticed any seat of the pants difference... my seat is not very sensitive.. my X5 is slow (even on premium) since it is 4700 lb and 225 HP and my Mustang is fast since it is 3400 lb and 475 HP.. I have a hard time noticing a little hp loss on the X5 with those two reference points. My my real question was does anyone notice knock with regular gas. Sounds like the answer is no and it is safe to give regular a try. I'll likely still run premium from time to time (hot weather) but not always.

It is safe to use regular IMO, that is what the knock sensors are for. I have used 87 regular in my 3.0 on occasion, but I do notice a performance decrease. I use 89 (plus) 95% of the time, with absolutely no performance decrease or fuel consumption increase over 91 premium.

If you think back to (non-modified) vehicles built prior to the onset of engine management computers, they didn't ping all the time. They could ping on a hill, for instance, at a certain throttle setting, if the AKI was too low for the conditions. Usually it indicated deposit buildup which caused hot spots. If the X5 computer is retarding the timing for the occasional onset of pre-detonation, it isn't doing it all the time but rather under certain conditions of engine load.

Remember that BMW specifies 91 to cover themselves, given the very wide range of fuel qualities in different regions.

The 89 in my area may be of a higher quality than in other areas. I know that when I travel and don't know the local suppliers, I am safer using 91. In those instances, it isn't worth the hassle.

I also agree with the other posters that there is little cash saving. In my area, 89 is $0.06/litre cheaper, and with a tank of 80 litres that is under $5.

Now for a question: How many here believe BMW on the 91 octane issue, but don't believe BMW on the 15,000 mile oil change interval? :)

From what I read on the pre '04 engines they are designed to run all the way down to 85 Octane without serious issues just a reduction in performance as has already been mentioned.

Ran my '01 on 87 every other tank and never had a problem with it, it passed all the maintenance checks fine up until it was lemoned at 30K miles for the fuel tank problem.

Most engines today are pretty sturdy under pressure, you may have some valve pitting due to some pre-ignition problems but after leaded engines became history engine technology has improved dramatically.

Take driving in Africa where fuel can be dubious in quality and yet you have a lot of older cars still running no problem.

In Europe they are adding cooking oil to their diesel to minimize the costs over here as the cost of cooking oil is so cheap and apparently as long as you do it in moderation there is very little impact to the engine. :wow:

BTW anyone have the Octane conversion for European to US, I believe 95 is the same as 91 and 98 is actually more like 93. They believe in more expensive cleaner burning fuels in Europe, methinks. My '05 4.4 runs fine on 95, no performance or mpg issues.