An interesting note about high octane
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Post Fiend
Joined: Nov 2002
Posts: 9,987
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From: Memphis, TN
An interesting note about high octane
This is off the Ford service CD:
Rough idle, hesitation, poor throttle response, induction backfire and stalls during cold start/warm-up may be caused by the poor volatility of some high octane premium grade unleaded fuels (91 octane or higher ([R+M]/2). When compared to regular grade unleaded fuel (87 octane), high octane premium grade unleaded fuel may cause long crank time.
Use a regular grade unleaded fuel in all vehicles, except where a premium unleaded fuel is recommended in the Owner Guide. If lean air-fuel type symptoms are experienced, determine the grade and brand of fuel used and offer the following service tips.
- Advise those using a higher octane grade fuel to switch to a regular grade unleaded fuel. For those using a regular grade fuel, advise them to try another brand.
- Do not advise using a higher octane unleaded fuel than is recommended for that specific engine. Ford engines are designed to perform best using a high quality regular grade unleaded fuel.
- Advise using a higher octane unleaded fuel to avoid potentially damaging spark knock or ping, but do so only after mechanical repairs are ineffective.
NOTE:
All unleaded gasolines used should contain detergent additives that are advertised as having "keep clean" or "clean up" performance for both intake valves and fuel injectors.
Rough idle, hesitation, poor throttle response, induction backfire and stalls during cold start/warm-up may be caused by the poor volatility of some high octane premium grade unleaded fuels (91 octane or higher ([R+M]/2). When compared to regular grade unleaded fuel (87 octane), high octane premium grade unleaded fuel may cause long crank time.
Use a regular grade unleaded fuel in all vehicles, except where a premium unleaded fuel is recommended in the Owner Guide. If lean air-fuel type symptoms are experienced, determine the grade and brand of fuel used and offer the following service tips.
- Advise those using a higher octane grade fuel to switch to a regular grade unleaded fuel. For those using a regular grade fuel, advise them to try another brand.
- Do not advise using a higher octane unleaded fuel than is recommended for that specific engine. Ford engines are designed to perform best using a high quality regular grade unleaded fuel.
- Advise using a higher octane unleaded fuel to avoid potentially damaging spark knock or ping, but do so only after mechanical repairs are ineffective.
NOTE:
All unleaded gasolines used should contain detergent additives that are advertised as having "keep clean" or "clean up" performance for both intake valves and fuel injectors.
