Fuel System - Regular Unleaded Fuel Usage

90cadillac15
NO.: 91-I-23

DATE: Dec. 1990

GROUP: 6C

CORP. NO.: 916304R
SUBJECT: REGULAR UNLEADED FUEL USAGE


This bulletin replaces DSIB 90-I-20 which should be discarded. This bulletin is being revised to include 1991 models.

Use of premium unleaded fuel is required on 1990 4.5L and 1991 4.9L Devilles, Fleetwoods, Eldorados, and Sevilles. In some areas premium unleaded fuel (minimum of 91 octane) may be unavailable. To allow the vehicles to operate with regular unleaded fuel the base ignition timing must be retarded from 10~ to 6~ BTDC. Retarding the initial timing will have a small adverse effect on composite fuel economy and performance.

Retarding timing for use with regular unleaded fuel has no effect on:

^ Durability
^ Engine cooling
^ Idle stability

Vehicles should be returned to proper timing when premium unleaded fuel becomes available.