I have always been curious as to what happens if you use regular or mid-level gas in a luxury car like an Infiniti or mercedes, audi, etc. I don't intend on doing it because I love my M35x too much (so please refrain from smart comments like "you shouldn't drive or buy an infiniti if you are going to use cheap gas" I know this). Will you damage the car or have to wash out the entire engine? What happens? I'm curious.

Define "cheap" gas -

If you are refering to lower octanes, using a fuel with an octane rating below what the manufacter calls for is generally not that good for your engine, even though new engines have knock sensors and adavnced systems that can adjust when a lower octane fuel is detected.You lose engine power and mpg's, but in the end it doesn't really hurt the engine.

If you are refering to bargain brand stations and the like, all gasolines are required to meet EPA standards for refining and detergent levels. However, not all gas is created equal. All fuel that you buy is ok for your car and it will run, however, certian brands use higher levels of detergents to help keep the engine from building up with crap deposits in it. Check this website out -

http://www.toptiergas.com

Many major auto makers cite certian stations as having good fuel for engines. In the end, all gas is ok for your car, just some brands do a better job cleaning up than others.

I mean regular or mid-range. I use the word cheap (maybe I should have said cheaper) because it less expensive in comparison to Premium.

I always thought there would be a problem with suddenly switching from premium to regular or mid-grade. And is there a major difference between premuim and mid-grade?

Ahh. For future reference, I would use "cheap" to describe something that is lacking in quality and "less expensive" to describe something that is...well...not as expensive. There can be a lot of misconception around those words

The difference from premium to mid-grade is the addition of regular. Mid-grade fuel is a blend of the premium and the regular tanks that the gas station have, creating a fuel with an octane level somewhere in the middle. This is better than just regular for a car that wants premium, but not as good as putting premium in. Again, your car can recognize this when it is put in and automatically adjust to the new fuel - it won't harm your engine.

Here in the SE, we've had a premuim fuel shortage and for the past 2 tank fulls, I've had to run 87. anything higher coud not be found. My mileage did not noticable decrease but I could tell it would lag to downshift when I needed it and when it finally did, I could hear it ping.

I even added a bottle of octane booster but the label indicates it will only increase the octane by 3 points. Now that I've been back to 93 for a week, I can still hear a ping but it downshifts as it did before using 87. I'll add a bottle of BG-44K and then another octane booster with my next tank of 93 & report back.

No! Don't use octane booster! Bad bad bad! Read your manual - it says not to use any aftermarket fuel additives as they can be horrible for your engine. Also, 3 points = .3, so you've only affectively raised it to 87.3...

Run the 87 as is. When you can get back to 93, just go from there...

i think the answer to your question was given above. If you use lower octane gas, you will just have less power available, but our car is "smart" and changes how the engine runs to match the octane. I think this was more of a problems on older cars where the knock sensors were not good, or just not present.

Gas stations need to get rid of "MID" grade gas it serves no purpose. there should only be regular and Premium. Most people with economy cars put in reg, and people with luxury cars/ sports cars will almost always put in premium. I don't even know anybody that puts in Mid Grade.

lower octane gasoline can cause your engine to ping and knock and cause damage to the engine in the future. in the owners manual premium fuel is recommended for the m45 and regular can be used in the m35 but premium is a recommended also. the higher the octane the more it will resist knocking. i personally use shell 93 in my m45 cause shell is a quaility brand and it has 5 times as much additve in its fuel than the government requires meaning it can clean youe fuel system and keep it clean with continuous use.

Having owned exotic and high performance cars over the years, I have run 87 octane in all my daily drivers and have noticed zero difference unless the car is driven spiritly...

If you drive your car with a heavy right foot and keep the rev's in the higher rpm band, then Premium Gas is highly reccomended. When I was the Infiniti Dealer for my big 30K service, they told me that hardly any of their customers use Premium as these engines are used across the Nissan range and designed to notice detonation with ease and retard the engine in micro seconds.

I ran a very high performance car for several weeks due to a premium shortage a while ago and there was no difference in driveability as I am a gently daily driver who never rushes to get anywhere aka boring LOL

However on weekend toys when owned, I always run Premium as these cars are usually driven on the Track. If you add a tune or make performance upgrades then yes it might be worth switching to Premium.

Just my 2c

About 6 months ago, my mom drove my car and when she was done she fueled it for me....thanks mom! but she also filled it with 87 octane....thanks mom! I drove it and It felt very sluggish. At first I thought it was my imagination but when I tried to floor it, the acceleration was nil. I went to my local autoparts store and added octane booster...it probally didn't help but it eased my mind. Im sure no damage was done, but all around the car didn't feel like itself.

As mentioned above, Premium or Octane Booster will certainly improve the performance of any vehicle. I am sure that most manufacturers don't reccomend Octane Booster as it can play havoc with O2 and fuel sensors down the line. I had a car when I had to replace several sensors over pro-longed use of Booster including the ECU as we thought this was incorrect when sensors kept going.

Having a warranty does help, although these additives can make the engine to run much richer.

The manual ('06 M35x) does say the engine can be safely run on regular but "recommends" premium. I've run the engine mostly on premium but also on mid grade a number of times and I can't see, nor feel, nor hear any indication the engine is aware of any difference?

It would probably run just fine on regular w/out problems as suggested by Infiniti. But why buy a premium machine and run it on regular? Or did someone already say that..?

I run regular almost exclusively, have for 60,000 miles. Unless you want to squeeze out that last 5 Hp there is no need to spend the extra money. The computer will make the adjustments, it’s not “cheaper”, it’s not “dirtier” it doesn’t have less quality control. I even lost a bet with my wife. When we first got it I wanted to run premium, I told her that the increased mpg would make up the difference in price. We averaged two tanks of each and noticed a 1mpg improvement on premium. Hardly worth the price. In fact the ability to run regular in the M was a deciding factor in my wife’s choice of it over the BMW.

MagicM wrote:Gas stations need to get rid of "MID" grade gas it serves no purpose. there should only be regular and Premium. Most people with economy cars put in reg, and people with luxury cars/ sports cars will almost always put in premium. I don't even know anybody that puts in Mid Grade.

Funny, my 94 Chrysler LHS manual said to run 89 or higher, which is mid-grade, yeah, that's not a purpose. Also, years before e10 was standard, and mandated in many states, you could get 89 octane e10 at Casey's gas stations for maybe a cent more (or maybe a cent less) than their standard 87 octane, assuming your car was designed for it (strangely enough, said 94 LHS was), once again, clearly no purpose. Also, some Sunoco stations have 86 through 94 in 5 or more different grades, this is because different vehicles, especially customized ones, will reach peak performance at different octanes (and also for dishonest marketing reasons, given they sell 86 for what everyone else sells 87 for), clearly these aren't purposes. Moreover, I have heard of (but have not seen) the option to choose your ethanol percentage at some gas stations. Where this isn't available, some people even blend e85 and regular gasoline to get a different ethanol percentage. The reason? They think their vehicle gets peak mileage somewhere less than 85% and greater than 10% ethanol. I don't know whether or not anyone does that with octane grades of gasoline, but clearly that wouldn't be a purpose either. Anyway, I don't have a cell phone, so perhaps we should ban cell phones, since they obvously serve no purpose to me. In other words, you don't have to buy the 89, and it doesn't negatively affect you in any way, so why gripe about it, and why act like it has no purpose just because it has no purpose to you?

lucygray wrote:I m planning to purchase a new car now please suggest me some new cars........

You should buy a Buggati Veyron, or maybe you should tell people what you are looking for in a vehicle in a using a forum that isn't specific to one model of one brand of car...

I'll take the other extreme and suggest a 73 Ford Pinto.