2007 Lexus LS460 8 Cyl, can 87 octane gas cause a 91 octane engine to give a P0171 code?

Question

Recently started getting check engine light and a check VSC message. Mechanic looks at it, resets computer, and all is good for 10-14 days. Then message reappears.

Regular gas (87 octane) may have been put in by a friend. Mixed with 93 octane.

Answer 1

87 okay, over at the fuel door if a higher octane is required it would be listed on the fuel door. You can even use fuel that contains ethanol provided that the fuel rail is updated from Lexus Recall. for the fuel rail. This type of engine has 2 MAF (mass airflow) on each side of the Bank. Do a MAF cleaning on both the left hand and the right hand Bank. Because its good for 14 days since engine light was cleared chances are the MAF cleaning may help resolve the lean code