Hey guys, I was kind of curious about the engines in the following aspects:

1) Gas mileage/power ratio? I know you guys will say to ONLY run premium fuel (91 octane in socal) but due to the economy and my empty pockets, ive been running the lowest octane (87) in my IS250 and its still fine. Which engine will adapt better to the low octane, yet still deliver most of mpg and performance that its rated at?

2) Longevity/Reliability? I know these engines have been around since the w203, so what are your guys's experiences? Which engine will last longer and be more reliable?

3) Performance? I know that they werent meant to be drag racers, but which car overall feels like it makes most use of the power given? Like does the c300 feel like it delivers 228 hp? the C350 and its 268?

Keep the responses coming!

 

GO BIG OR GO HOME

 

300 is better if you want to go slow/350 is better if you wanna go faster

 

why didnt you vote on the 350 then?

 

They are almost the same the aditional 40 hp is not big difference you barely notice them. I just chose the C350 because the equipment and looks (rims, lid etc)

 

Stop running 87 octane. You'll have problems with idling pre-ignition, which involves firing a piston into the rod, rod into the crank, while the crank has to continue to push the piston along with the force from the other pistons, which seriously dampens your power and ultimately your fuel economy.. which will negate any 2% cost savings from not spending that extra dime or less on the correct octane. You can throw in your service check engine light that will eventually appear, and toss in the risk of the dealership voiding your engine warranty.

I'll keep tuning on my 350 until I've got it putting out around 350 hp.

 

If youre on that much of a budget then I don't think buying the bigger engine then not being able to afford to fill it is the best option for you IMHO

 

They look the same..Both come with Ugly 17" rims and you couldve added the spoiler to a C300 like I did.

 

While I agree he should use the correct octane..this post is def a bit extreme. None of that is likely to happen as a result of using 87 octane.

 

Oh..and the 300 gets my vote because the 350 doesn't offer a manual..nor is it fast enough to justify the price..the 335i and the new $44k supercharged Audi S4 blow it away.

 

Using the wrong octane, means the wrong combustion temperature, means improper ignition, means incorrect gas expansion, means short piston throw, means cam timing wrong, means loss of power is immediate, means fuel economy is decreased. Also, idling, a relatively benign action, is probably the hardest thing for an engine to do when running on too low of an octane.

Dealership voided warranty? It's clearly stated that using the wrong octane may void your warranty.

Here's an interesting article I found on Octane Requirements:
http://www.faqs.org/faqs/autos/gasol...section-1.html

tl;dr

1. The use of fuel of too low octane can actually result in both a loss of fuel economy and power, as the management system may have to move the engine settings to a less efficient part of the performance map. The system retards the ignition timing until only trace knock is detected, as engine damage from knock is of more consequence than power and fuel economy.
2. An increase in Compression Ratio will require an increase in fuel octane for the same engine design. Increasing the compression ratio increases the theoretical thermodynamic efficiency of an engine. Note the C350 has a 10.7:1 CR and the C300 has a 11.3:1 CR. Without the ECU, this would require appx 103 and 105 octane fuel respectively.
3. Section 7.4 also notes that using 87 octane instead of 91 will retard the spark ignition advance over 5 degrees, which significantly affects flame composition and fuel consumption.

 

if you factor in the spoiler, rims, and P1 package, and larger brake discs, then the difference doesnt come out to be that big.

 

I apologize in advance for being blunt, but if you dropped $35k+ on a car (these can even be spec'ed up to the $42-$45k range), and are trying to cut corners by saving money on the gas, your doing yourself a disservice as others have mentioned. Not only are you losing gas mileage (with either engine I might add), but your doing long term damage - and yes, MB can void your warranty. There's a reason MB recommends 90 or 91 as a minimum and if you couldn't afford the gas, perhaps you purchased the wrong vehicle.

Its like those who purchase these cars and complain about the price for the Service A's and B's. I asked the dealership the cost for these before making a purchase, crunched my own numbers and went with a car I could afford. I suppose its the same type of thinking that caused our entire mortgage overextension situation we are in now. People inherently overextending themselves purchasing $500k+ homes with minimal income and no down payment towards the mortgage. Gee, I wonder what will happen... Foreclosures, defaults, and debt as high as the sky...oh my!

 

I think that goes without saying.

 

what?!?!?!

 

Really comes down to which options you want. If you want 4matic, your only choice is the C300. If you want a manual transmission, your only choice is a C300 Sport. If you want Black Maple Walnut interior trim, your only choice is a C350. If you want a Luxury model, your only choice is a C300. Off the top off my head, those are just about the only differences, there used to be more such as wheel packages, but thats all been addressed for the 2010 model year.

By the way, the C300 when equipped with 4matic (automatic transmission is standard on 4matics) is just adequate. That much added weight could really use a few more hp to pull itself along. To that effect, the car magazines have said the same thing about the C350, in that it really needs 300hp just to compete with its competition. You just need to test drive them both and figure out which meets your needs.

 

Good thinking.... very true.

 

Well said! I voted for the 300 because with the manual transmission, its more than adequate...its quite enjoyable and I don't care who else goes faster. I'm not racing...I'm having a good time driving MY car. And, with 20's in the city and reaching 30mpg on the highway, I also smile at the gas pump. So, my vote goes for best overall balance.

 

Is that the new SLR ? that car is sick!!

 

Well guys, I leased my IS250 in Jan. 07, when i had a good paying job. Now that im laid off, im pretty much broke so im forced to pump 87. Also, im just curious, but how big a difference is there from 87 -89 -91? 89 being the one below premium, but above regular. If im broke like i am now, would 89 be ok enough, or is not much better than 87?

 

Also, when times are hard and i cant afford premium, which engine will better adapt to the low octane? i know the 300 engine is flex fuel E85 so is that one more compatible to lower octane than 350 engine?

 

This is complete crap - please ignore

Please run your car on premium fuel or it will tend to run with it's timing retarded everytime you load the engine.

 

Not to sound demeaning or anything, but I COMPLETELY AGREE with the statements above. I really don't understand why people buy Mercedes-Benz or other luxury and/or performance cars that are made to run on Premium 91/93 Octane Gasoline, and put Regular 87 Octane Gasoline in it because they can't afford the correct gasoline. IMHO, if you CANNOT afford to put the correct 91/93 octane gasoline in your Mercedes-Benz (which is probably on average $0.20/gal more, or LESS THAN $4.00/tank), then you probably aren't getting the car best suited to your needs.

Honestly, worst case scenerio, $4.00/tank is probably around $4/week (if your commute is around 300-400 miles per week) to $12/week (if your commute is 900-1,200 miles per week)... which equals somewhere between $16-$48/month... which equals somewhere between $192-$576/year. If you aren't able to get buy filling up on premium because you're spending an extra $4-$12/week, $16-$48/month, and $192-$576/year, then you have A LOT more to worry about than which Mercedes-Benz you should buy (C300 or C350)!

Perhaps a more fuel efficient and affordable car like the Honda Civic or Toyota Corolla (either preowned or new) would better suit your needs. Not only would you save money by using Regular 87 Octane Gasoline (as the car manufacturer intended), but you would NOT run the risk of damaging your vehicle over time, or voiding the manufacturer's warranty (if they ever found out and felt like enforcing this clause), or operate at sub-par power levels and sub-par gas mileage... and you would also SAVE TENS OF THOUSANDS OF DOLLARS on your vehicle purchase/loan, which could be put into other more important things (like more gasoline, or food, or rent/mortgage, or credit card bills, or your savings account so you don't have to worry as much about money in this recession, or whatever)!


EDIT: Now if you already BOUGHT a Mercedes-Benz (when times are good), and then everything went to heck and you need to give up a lot of luxuries (including selling your house, your boats, your extra cars, your jewelery, your vacations, and cut down to only the bare essentials)... THAT can be understandable. But PLANNING TO BUY a brand new Mercedes-Benz and ALREADY PLANNING to always gas it up with Regular 87 Octane... THAT is just stupid IMO...

 

The C350 is more economical than the C300 in most on-road circumstances. The C300 engine is slightly smoother running than the 350. USA models are constrained by options available as mentioned above. They will have equal life. WTF are you talking about regular fuel !!!!!

We have a C350 Elegance Auto - full leather, BiX, Parktronic etc. Happy with the vehicle.

 

While I agree in that the loss in mpg offsets the lower cost of the fuel, you are going a bit (ok a lot) too far.

At idle the engine basically under very little load. A car tuned for 91 will easily idle on 87 without even a hint of detonation or pre-ignition. If he is loading the motor heavily, then yes, the computer will pull a bunch of timing. For normal driving, he will likely notice no difference.