Fuel; Fuel Requirements - Subaru Ascent 2023 Manual

7-1. Fuel

CAUTION
. Use of a fuel which is low in
quality or use of an inappropriate
fuel additive may cause damage
to the engine and/or fuel system.
. Some gas stations, particularly
those in high altitude areas, offer
fuels posted as regular octane
gasoline with an octane rating
below 87 AKI (90 RON). Use of
those fuels is not recommended.
& Fuel requirements
The engine is designed to operate using
unleaded gasoline with an octane rating
of 87 AKI (90 RON) or higher.
NOTE
When towing a trailer, SUBARU recom-
mends using unleaded gasoline with an
octane rating of 91 AKI (95 RON) or
higher to reduce the risk of engine
overheat.
! Fuel octane rating
Using a gasoline with a lower octane rating
can cause persistent and heavy knocking,
which can damage the engine. Do not be
concerned if your vehicle sometimes
knocks lightly when you drive up a hill or
when you accelerate. Contact your
SUBARU dealer if you use a fuel with the
specified octane rating and your vehicle
knocks heavily or persistently.
! RON
This octane rating is the Research Octane
Number.
! AKI
This octane rating is the average of the
Research Octane and Motor Octane num-
bers and is commonly referred to as the
Anti Knock Index (AKI).
! Unleaded gasoline
The neck of the fuel filler pipe is designed
to accept only an unleaded gasoline filler
nozzle. Under no circumstances should
leaded gasoline be used because it will
damage the emission control system and
may impair driveability and fuel economy.
! Reformulated gasoline
SUBARU supports the use of reformulated
gasoline when available. Reformulated
gasoline has been blended to burn more
cleanly and reduce vehicle emissions.
! MMT
Some gasoline contains an octane-enhan-
cing additive called MMT (Methylcyclo-
pentadienyl Manganese Tricarbonyl). If
you use such fuels, your emission control
system performance may deteriorate and
the CHECK ENGINE warning light/Mal-
function indicator light may turn on. If this
happens, return to your authorized
SUBARU dealer for service. If it is deter-
mined that the condition is caused by the
type of fuel used, repairs may not be
covered by your warranty.
! Gasoline for cleaner air
Your use of gasoline with detergent ad-
ditives will help prevent deposits from
forming in your engine and fuel system.
This helps keep your engine in tune and
your emission control system working
properly, and is a way of doing your part
for cleaner air. If you continuously use a
high-quality fuel with the proper detergent
and other additives, you should never
need to add any fuel system cleaning
agents to your fuel tank.
Many gasolines are now blended with
materials called oxygenates. Use of these
fuels can also help keep the air cleaner.
Oxygenated blend fuels, such as ethanol
(ethyl or grain alcohol) may be used in your
vehicle, but should contain no more than
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Fuel