# Using medium or low octane instead of high test **URL:** \ **Category:** Power/Fuel\ **Tags:** gasoline\ **Created:** [June 3, 2008, 8:24pm UTC](https://community.cartalk.com/t/using-medium-or-low-octane-instead-of-high-test/14803 "2008-06-03T20:24:34Z")\ **Posts on this page:** 14\ **Page:** 1
**Author:** ![wmharris](https://avatars.discourse-cdn.com/v4/letter/w/f9ae1b/32.png) [@wmharris](https://community.cartalk.com/u/wmharris)\ **Post date:** [June 3, 2008, 8:24pm UTC](https://community.cartalk.com/t/using-medium-or-low-octane-instead-of-high-test/14803/1 "2008-06-03T20:24:34Z")
I drive a 2003 Mercedes C230 Kompressor Coupe which, even on the gas gauge says to use ONLY premium gasoline. My mechanically minded friends say it really doesn’t matter with today’s engines, but then say, well, maybe because it is super-charged I should still use premium (it’s a political year and everyone waffles!). I’d love to save some money (I live in LA and premium is now $4.599 per gallon down the block) but I don’t want to ruin the engine/exhaust/etc.! So, what’s the verdict, can I use regular or even the mid-grade gasoline without harming the car? (Would it make a difference if the car wasn’t turbo- or super-charged? ---
**Author:** ![wizard](https://avatars.discourse-cdn.com/v4/letter/w/a87d85/32.png) [@wizard](https://community.cartalk.com/u/wizard)\ **Post date:** [June 3, 2008, 8:30pm UTC](https://community.cartalk.com/t/using-medium-or-low-octane-instead-of-high-test/14803/2 "2008-06-03T20:30:30Z")
Use what the manufacturer recommends. The possible repairs on this make of car using a cheaper gas will be a lot more expensive than what you will be may save. ---
**Author:** ![mcparadise](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/mcparadise/32/32_2.png) [@mcparadise](https://community.cartalk.com/u/mcparadise)\ **Post date:** [June 3, 2008, 8:37pm UTC](https://community.cartalk.com/t/using-medium-or-low-octane-instead-of-high-test/14803/3 "2008-06-03T20:37:45Z")
Your engine needs premium. There’s no way I’d feed a super-charged engine anything else. It might make a difference if the engine wasn’t super-charged, but it is, so it doesn’t matter. You own a premium car with a high performance engine. Buying premium fuel is part of the bargain, and it always will be. ---
**Author:** ![Jeremy\_R\_Hoyt](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/jeremy_r_hoyt/32/37_2.png) [@Jeremy\_R\_Hoyt](https://community.cartalk.com/u/Jeremy_R_Hoyt)\ **Post date:** [June 3, 2008, 8:43pm UTC](https://community.cartalk.com/t/using-medium-or-low-octane-instead-of-high-test/14803/4 "2008-06-03T20:43:31Z")
As long as Mercedes went through all that trouble to take the guesswork out of it, you should use premium gasoline. ---
**Author:** ![the\_same\_mountainbike](https://avatars.discourse-cdn.com/v4/letter/t/c89c15/32.png) [@the\_same\_mountainbike](https://community.cartalk.com/u/the_same_mountainbike)\ **Post date:** [June 3, 2008, 8:47pm UTC](https://community.cartalk.com/t/using-medium-or-low-octane-instead-of-high-test/14803/5 "2008-06-03T20:47:46Z")
Premium. Period. It never ceases to amaze me that people spend oodles of hard earned cash to get a rocket ship of a car and then want to scrimp on gas expense. If you’re on a budget and need to worry about the cost of gas you should consider something a lot more affordable than a C230 Kompressor Coupe. ---
**Author:** ![hammrs1](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/hammrs1/32/808_2.png) [@hammrs1](https://community.cartalk.com/u/hammrs1)\ **Post date:** [June 3, 2008, 8:50pm UTC](https://community.cartalk.com/t/using-medium-or-low-octane-instead-of-high-test/14803/6 "2008-06-03T20:50:07Z")
theres not that big a diirenace in the price compared to possible damage and probably worse fuel mileage with the cheap stuff. ---
**Author:** ![SteveF](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/stevef/32/2_2.png) [@SteveF](https://community.cartalk.com/u/SteveF)\ **Post date:** [June 3, 2008, 9:09pm UTC](https://community.cartalk.com/t/using-medium-or-low-octane-instead-of-high-test/14803/7 "2008-06-03T21:09:45Z")
Make a list of the wackos who tell you it’s OK to use a lower grade of gas. Now you know who NOT to trust for automotive advice. ---
**Author:** ![JoeMario](https://avatars.discourse-cdn.com/v4/letter/j/3bc359/32.png) [@JoeMario](https://community.cartalk.com/u/JoeMario)\ **Post date:** [June 3, 2008, 9:30pm UTC](https://community.cartalk.com/t/using-medium-or-low-octane-instead-of-high-test/14803/8 "2008-06-03T21:30:25Z")
Be careful, it can easily cost you most more money to use mid-grade or regular gasoline. If your car gets around 20 mpg and you’re saving 10 cents/gallon to drop to mid-grade, then all it takes is a loss of 1/2 mpg for this switch to begin costing you more money. Do the math for yourself. ---
**Author:** ![JoeMario](https://avatars.discourse-cdn.com/v4/letter/j/3bc359/32.png) [@JoeMario](https://community.cartalk.com/u/JoeMario)\ **Post date:** [June 3, 2008, 9:39pm UTC](https://community.cartalk.com/t/using-medium-or-low-octane-instead-of-high-test/14803/9 "2008-06-03T21:39:33Z")
[Ignore - deleting duplicate reply] ---
**Author:** ![Craig58](https://avatars.discourse-cdn.com/v4/letter/c/3da27b/32.png) [@Craig58](https://community.cartalk.com/u/Craig58)\ **Post date:** [June 3, 2008, 9:40pm UTC](https://community.cartalk.com/t/using-medium-or-low-octane-instead-of-high-test/14803/10 "2008-06-03T21:40:01Z")
Another vote for premium. I assume you know the cost of work on your engine. ---
**Author:** ![ken\_green](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/ken_green/32/816_2.png) [@ken\_green](https://community.cartalk.com/u/ken_green)\ **Post date:** [June 3, 2008, 11:33pm UTC](https://community.cartalk.com/t/using-medium-or-low-octane-instead-of-high-test/14803/11 "2008-06-03T23:33:00Z")
Fuel of too low an octane causes your engine to “ping” or cackle from burning too lean. This also increases the cylinder temperature and bigger problems will result. One can see this in practice in a light plane like a Cessna 180 which has the fuel/air mixture changeable by the pilot. When it’s too lean you can watch the exhaust manifold temp gauge rise dramaticaly and then adjust as needed. The only adjustment you get in your computerized car is the fuel octane choice. Adhere to the owners manual specs always but don’t buy gas from some hole-in-the-wall station even so. Even at these high prices the el-cheapo gas is still the same crap it always was before. keeping you car running right in the first place will ALWAYS cost you less than fixing it. ---
**Author:** ![bscar](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/bscar/32/34_2.png) [@bscar](https://community.cartalk.com/u/bscar)\ **Post date:** [June 3, 2008, 11:51pm UTC](https://community.cartalk.com/t/using-medium-or-low-octane-instead-of-high-test/14803/12 "2008-06-03T23:51:30Z")
I agree. If the OP wants to use regular, I’d be more than happy to trade them, even up, for my Civic, unless they have a loan on it ---
**Author:** ![pleasedodgevan](https://avatars.discourse-cdn.com/v4/letter/p/51bf81/32.png) [@pleasedodgevan](https://community.cartalk.com/u/pleasedodgevan)\ **Post date:** [June 4, 2008, 4:55am UTC](https://community.cartalk.com/t/using-medium-or-low-octane-instead-of-high-test/14803/13 "2008-06-04T04:55:53Z")
If your engine didn’t require premium if it wasn’t turbo or supercharged, your manual would let you know. I would have to “check the book” to know. I would not guess. ---
**Author:** ![andrew\_j](https://avatars.discourse-cdn.com/v4/letter/a/91b2a8/32.png) [@andrew\_j](https://community.cartalk.com/u/andrew_j)\ **Post date:** [June 4, 2008, 11:24am UTC](https://community.cartalk.com/t/using-medium-or-low-octane-instead-of-high-test/14803/14 "2008-06-04T11:24:48Z")
The differential you pay from premium to regular is the absolute cheapest it has been in years. Currently it averages 6% extra for premium as the price is fixed pretty much at $0.20 more when fuel was $1, $2. $3 or even now $4/gallon more. You should be happy you don’t pay much more for it now 🙂