| Anyone ever put regular unleaded when the manufacturer specified premium? What happened??? |
| Lower performance. Modern engines have a knock sensor that detects low octane and will reduce engine output. Most likely to notice it when engine is under strain like going up a big hill. |
| Is it true you only need it if manufacturer says “required” but not if “recommended?” |
Yes, unless you hear knocking, notice performance issues, or notice a drop in gas mileage. Then go to a higher level. |
It doesn’t “reduce” output. It retards timing. That, under unusual circumstances (typically at a part of the powerband you don’t ever use) MIGHT reduce power. Generally though, the caution that it me reduce engine performance relates to MPG. |
| With regular I had knocking so I moved up. Premium was recommended but I wanted to find out for myself. |
| I use both.. Ends up being every other fill. When I go to Costco I fill up on premium. Otherwise regular. 10 years or so. No issues.. I don't really track mileage. |