The 2018 GMC Sierra uses regular unleaded fuel with an octane rating of 87 or higher. The Sierra's regular cab holds 28.3 US gallons, and the Double and Crew Cab sizes hold 24 US gallons. The Sierra offers a combined mpg of 17-20; 15-18 miles per gallon in the city and 20-24 miles per gallon on the highway. Vehicles requiring premium fuel with an octane rating of 97 or higher use it to maintain proper firing. In general, an expensive car is designed to need more compression in its combustion chamber. Switching to premium in a truck designated for regular fuel will not improve its performance and even might harm the engine over time. Follow the manufacturer's recommendations to keep the Sierra running smoothly.
Gretta K
November 17, 2020
A 2018 GMC Sierra 1500 truck only needs to use regular 87 octane gasoline.
Eric S.
August 29, 2019
It would seem that with the 2018 GMC Sierra trucks, those that have the same engine size take the same type of fuel. The 5.3 liter engine models, the Sierra crew cab 6.5FT SB, the SLT crew cab 5.8FT SB, the SLT double cab SB, the SLT crew cab 6.5FT SB, the SLE crew cab 6.5FT SB, the Denali crew cab 5.8FT SB and the Denali crew cab 6.5FT SB all use regular unleaded gasoline. The 4.3 liter engines can use either E-85 or regular unleaded gas. That makes these models Flex Fuel vehicles. The trucks that are Flex Fuel are the Sierra double cab SB, the Sierra regular cab SB and LB, the Sierra crew cab 5.8 SB, SLE regular cab SB and LB, the SLE double cab SB and the SLE crew cab 5.8 SB.
I used 87 on my 2018 denali but just read manual and realized I should be using premium. What should I do for my next refuel ?
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