Can you put midgrade89 or higher octane in a Mercury Topaz 1994?

Answer 1

Since the early 80's, most production vehicles have been "detuned" to reduce emissions. In the process, compression ratios have been reduced. As a result, those engines do not NEED higher octane fuel. If you do not have a high compression performance engine you do not NEED midgrade fuel even though the auto industry has entered into agreements with oil companies to try to persuade people to use the more expensive fuels. If you have the SHO or SC engine in your Topaz (did they even put those engines in a topaz?) then perhaps the higher octane will be better for you. Otherwise, to make sure your injectors function better, use FRESH fuel, in other words, buy fuel from a place that sells it fast and is constantly buying fuel from the refinery. That's a far better defense against injector problem than any additive or special fuel blend. If you don't hear pinging in your engine you don't NEED higher octane fuel. If you DO hear pinging and the engine is stock, you probably just need to have it timed.