Recommended Fuel; Engine); V6 Engine); Prohibited Fuels - GMC Cadillac CT5 2021 Manual

296 DRIVING AND OPERATING
Recommended Fuel (LSY
2.0L L4 Engine)
Premium unleaded gasoline meeting
ASTM specification D4814 with a
posted octane rating of 93
is highly recommended for best
performance and fuel economy.
Unleaded gasoline with an octane
rated as low as 87 can be used. Using
unleaded gasoline rated below
93 octane, however, will lead to
reduced acceleration and fuel
economy. If knocking occurs, use a
gasoline rated at 93 octane as soon as
possible, otherwise, the engine could
be damaged. If heavy knocking is
heard when using gasoline with a
93 octane rating, the engine needs
service.
Do not use any fuel labeled E85 or
FlexFuel. Do not use gasoline with
ethanol levels greater than 15% by
volume.
Recommended Fuel (LGY
3.0L V6 Engine)
(R+M)/2
Use premium unleaded gasoline
meeting ASTM specification D4814
with a posted octane rating of 93
(R+M)/2. If unavailable, unleaded
gasoline with a posted octane rating
of 91 may be used, but with reduced
performance and fuel economy. If the
octane is less than 91, the engine
could be damaged and the repairs
would not be covered by the vehicle
warranty. If heavy knocking is heard
when using gasoline rated at
93 octane, the engine needs service.
Do not use any fuel labeled E85 or
FlexFuel. Do not use gasoline with
ethanol levels greater than 15% by
volume.

Prohibited Fuels

Caution
Do not use fuels with any of the
following conditions; doing so may
damage the vehicle and void its
warranty:
For vehicles that are not
FlexFuel, fuel labeled greater
than 15% ethanol by volume,
such as mid-level ethanol blends
(16 50% ethanol), E85,
or FlexFuel.
Fuel with any amount of
methanol, methylal, ferrocene,
and aniline. These fuels can
corrode metal fuel system parts
or damage plastic and rubber
parts.