The Cadillac XT5 requires the use of regular unleaded gasoline, with an octane of 87 or higher. Studies show that the usage of premium gasoline in engines that don't require it is simply a waste of money; You'll gain no benefit from using 91 or better gas, because the XT5's engine's compression ratio simply does not call for it. On the other hand, You'll also not want to use gasoline with too LOW an octane, either. E-85 can harm the XT5's engine, because it may lead to engine knocking. Over time (even a short period of time), engine knocking can cause a significant amount of damage, up to and including totaling the vehicle. Therefore, You'll want to stick with the happy medium of 87, or at best, 89.
The owners manual states any gasoline at 87 octane or above. NO E-85, or methanol blends either. The manual also has a couple other chemical additives in gasoline you want to avoid. Basically, Lewis is correct. I found that I get better mpg's using Amoco 91 or 93 whichever the highest octane is. I've also tried Shell gasoline, again all octanes and my mpg's went down categorically. Don't know why Shell's performance was so poor.
Lou
July 30, 2023
The XT5 with the 3.6 V-6 uses (87 octane) regular fuel. The XT5 with the 4 cyl turbo requires 93 grade premium. Use of regular in this engine will lead to serious damage and even engine failure.
Lewis S.
April 9, 2020
Unlike other luxury vehicles that require premium gasoline, the cadillac xt5 can be filled with 87-octane regular unleaded fuel.
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