ALT-3 Premium Versus Regular Gasoline
There's always a debate about whether to pay extra for premium fuel. After a year where drivers like me in California have experienced US$4.50 per gallon prices and now rock bottom US$2.00 a gallon prices, I was forced to investigate every way possible to save money. I bought my car in May 2007 and had always used premium fuel as recommend by the manufacturer. As gas prices increased I read up on the subject and learned I could use the cheaper regular grade unleaded gas.
Beyond price, there are many factors but the first one is the age and type of car. Older cars, pre-1975 or so, it doesn't make a difference. If you have a real old car, you may need a lead additive as some engines were made to be lubricated by the lead in the gasoline. Many engines were rebuilt over the years to enable them to run on unleaded gas, as leaded gas disappeared in the early 1970's. Check with your mechanic or other expert before you make any changes.
I have a small 2007 Mercedes and although Mercedes and everyone else wants you to think you need premium fuel, the real story is a bit different. Mercedes sells cars around the world. Not all gas is the same, and not all qualities of gas are available at all times. The engine computer system in the car is very smart, it can sense the octane of the fuel and adjust accordingly for best mileage and performance. So if you use premium fuel, the computer knows and does offer better performance. If you use regular unleaded, the computer changes the engine settings accordingly, offering a bit less performance, but no damage to the engine or system.
Note this is not the case for E85, ethanol blend fuel. This cannot be combined with gas and there is a special way to use this in your car with regards to switching from it to regular gas and back again. The owners manual has a complete description for drivers who have access to this new fuel. I was in Las Vegas recently and was shocked to find a station selling E85 for $1.00 per gallon less than the cheapest unleaded gas. I almost pumped it in, thinking it was a simple swap. Fortunately, I remembered reading my owners manual upon purchasing the car and remembered there was a little more than just filling up with this new cheaper fuel. Drivers should also note the E85 burns differently, so you use a bit more fuel, you pay less per gallon but use more, so it evens the cost to equal gasoline.
Now I have noticed a drop in performance when using regular octane, lets say about 25%. Starts are slower and when passing or rapid acceleration, you do notice a decrease in responsiveness. So for me, with gas so cheap I can afford the luxury of premium, but when the price goes up, I'll sacrifice the performance to save money.
