EmceeSquared

Yo. So, I'm looking for advice from the performance enthusiasts/technicians in the audience. I get free 87 octane, but have to pay for anything else as part of a work reimbursement.

I'm thinking of going 87 all the time on my stock 2008 c350...any thoughts? Seems like it would just lack a little punch. My question is...can the dealer tell which fuel I'm using and would this affect my warranty. Any thoughts on long term performance should I want to go back to 93 because I'm getting pwned by a 2001 Maxima?

Thanks for your advice!

angeloxnet

let the flaming begin, some ppl on this forum are touchy about this subject, however there are many threads on this already! just search.

I stick with 91 octane, i follow the manufacturer recommendations.

chilledbenz

Yes the flaming shall begin...there has to be a reason more and more car companies are recommending higher octane in their engines. They do the tests, they know whats going on, if they have decided that only a certain octane should be used in their engines then that's what you should stick by.

Obviously filling the car up every once in awhile such as in an emergency with a lower octane isn't going to ruin your engine, but prolonged use may. If you decide to go this route and use only 87 octane and something with the engine should go bad, they can and will test the gasoline in your tank. The finding of a fuel not recommended by the manufacturer would be cause for a void of warranty and you would be left with the bill for any repairs. They aren't suggesting you use a higher octane, they simply put it in writing to do so.

I'm sticking with what is stated in the owners manual. I've seen the repair bills for these cars when something goes wrong, thankfully it's been under warranty, I'm not giving them any reason to void mine.

got_thang?

If you wanna fill up 87 octane why don't you just get a 08 chrysler serbring instead of buying a 08 C350...

trial0r

can someone post the exact language from the owners manual?

mac911

Put what the car recommends.

If the car calls for 87, don't waste money on 91.

However, when a call asks for 91 minimum, put the 91. They don't do it to take money from you, they do it because it's what the car is designed to use.

20 cents per gallon when the gasoline is as high as it is today, is a tiny percentage increase. Treat your car right.

Thats my opinion. Again, I use regular, when it is called for, but if a call asks for the premium, thats what it gets!

ColoradoDriver

If it is available near you, mix the 87 with one gallon of E85 for every 10 of gasoline. That way your octane will be fine, and you only have to pay for a couple gallons of E85 each tank.

narky

Forget the manual. When you open the little gas latch on the side, there's a sticker that says (on mine) "91 octane MINIMUM"

chilledbenz

Except as the owners manual says no E85 on C350's or C300 4matics.

Carsy

If I were in your situation where I could run my car with out any fuel costs in the present high price enviroment I would :-

1. Visit my dealers Service Manager & ask whether it is possible to detune my engine to run safely on 87.

2. If so, receive the answer in writing that my warranty will not be affected.

3. If not sell the MB ASAP to lessen depreciation costs & buy a car which will run on 87 & put the saved money into your retirement fund.

Fuel prices in the medium to long term are only going one way .Please tell me who you are working for & I will put in a job application .

Untertürkheim

Could you also clarify, do you have to pay the price differece for the premium, or then pay for it completely? If you only pay the diff, $3 per tank is nothing to worry about.

To answer your question, it is very easy for the service dept to tell what gas you are/have been running, and yes, it will void your warranty.

trial0r

+1

rs1985

why not do this
ask your company to pay for watever they will pay u
and you just pay the extra ?

AkaSigFreak

I have also been told that besides testing you gas in the tank the dealership can check the on board data log and determine ignition temp and that will determine what octane fuel you are running. It also logs how often the "knock" sensor kicks in which reflects lower octane fuel. If you get free low octane gas and want to use it, I would put in a bottle of good quality octane booster (even at $5-$10 a bottle still cheaper than filling up at $65+).
Just my 2 cents

ColoradoDriver

You did not understand. You would not be running E85 (i.e., 85% ethanol; 15% gas) in you Mercedes. Instead, I was saying if you mix in 10% with your 90% 87 octane gasoline, you will raise the overall octane a bit higher. If you started with pure gasoline you would only be ending up with the mix containing 8.5% ethanol--and that is less ethanol than the 10% ethanol most of us are forced to use in the gas coming from the local filling stations.

AsianML

Way too much work involved just to save a couple of bucks per tank.

MBTex

+1.

Pay the extra money for the proper feul. The fact that 91 is required isn't exactly an additional selling point for MB so they would tell you that 87 is okay if it were (at least informally anyway).

You'll save money by going with cheaper feul, but may get nailed in the long run if you have engine problems and your warranty is voided or expired.

If someone is worried about the extra 20 cents per gallon when buying the car, they should invest in a lesser expensive vehicle. Your situation is unique that apparently you are getting free gas so you would be saving $4.50 a gallon. I agree with the others and say see if you can just pay the difference.

maninblack

EmceeSquared

The difference is between paying $0 for gas and paying $65+ each fill up. This is a serious expense for me in the long term given other unexpected financial issues not foreseen when purchasing my luxury item = )

Manufacturers recommend a lot of ****. I'm sure that people here have plenty of modifications to their c350's that aren't manufacturer approved. I'd love for someone to find a real reason (besides voiding warrantee, which is a big deal of course...the reason I'm questioning this) in terms of engine wear or risk that makes this is a bad idea.

Trust me, I'd much rather have the 93 octane and not deal with the uncertainty of not knowing what I'm doing to my first real car!

mac911

Yeah this is a tough one.

Got to see if work let you pay the difference. Otherwise, maybe do like said and spend the $5-$10 per tank on octane booster, or maybe every other tank put it in, or pour half the bottle with each tank.

I'd never say put 87 in it, ever, but it's hard when it's completely free, if you do.

I still wouldn't do it daily, i'd try to pay the difference, or if not allowed, put something else in the tank to bring up the octane some.

Untertürkheim

The fact is that using fuel of too low of an octane will cause engine damage, which is the reason it will void your warranty. Carbon buildup will be one long term result, and you will have consistent pre-ignition, which could cause any number of issues.

maninblack

sorry , not trying to flame you , but looks like you cannot afford to drive this car , or any car that uses 91 octane

Carsy

A bombastic , unhelpful & very likely untrue statement. There is a way around this & I hope EM2 finds it.

maninblack

of course i am unhelpful , because this person has already made up is mine , no matter what happen , he will use 87 octane .. he just want someone here to back him up . lots of other member already tell him not to and he still dont get the message , let see how you can help him out

BlackC230Coupe

honestly, you can put 87 in there and it will drive ok for regular driving. if you start to floor it, then it will suck. it wont really effect the car, depending on how long you plan to keep it. Trust me, people put 87 octane in the Mercedes loaner cars all the time and they are fine.