Generally, no, you cannot use Unleaded Plus (mid-grade) in any car. While it won't damage most modern vehicles, it is often an unnecessary expense. The key factor is your car's octane rating requirement, which is specified by the manufacturer and found in your owner's manual or on the fuel door. Using a higher octane fuel than required, like Plus (typically 89 octane) in a car designed for Regular (87 octane), provides no meaningful performance, fuel economy, or cleanliness benefits. Your engine's computer is calibrated for a specific octane level, and it cannot take advantage of the higher anti-knock properties. However, if your car requires Premium fuel (91-93 octane), using Unleaded Plus is not recommended and can lead to engine knocking and potential long-term damage, as the lower octane is insufficient for high-compression engines.
For most cars that specify Regular unleaded, sticking with 87 octane is the most cost-effective choice. The only exception is if you experience persistent engine knock with Regular fuel, which could indicate a mechanical issue, but a switch to Plus might be a temporary fix until a mechanic can diagnose the problem. The rule of thumb is simple: follow the manufacturer's recommendation. It's designed to optimize your engine's performance and longevity. Paying extra for mid-grade fuel in a car designed for Regular is essentially paying for a benefit you will never realize.
