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1992 Sedan DeVille
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821 Posts
Discussion Starter · #1 ·
Is it ok to run regular in a DeVille with the 4.5 SFI engine? I was curious as the rising gas prices are quickly getting out of hand. I know the official recommendations say to use premium only. I was curious to what you guys run and recommend for your 1990 DeVille's.

Also Anyone with a 89-93 should have the same answer I believe.

Any questions or comments please feel free to post.
 

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1994 Cadillac Deville 4.9, 1995 mazda millena
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20 Posts
Yea gas is crazy now, but your engine has no knock sensor so it cant adjust the timing to compensate, i tried once in mine it was knocking a little but the timing is also advanced a little
 

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1992 deville & 1990 brougham
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12 Posts
I drive my 92 deville 4.9 daily and use the regular gas all the time. I have not heard of any knock or have not had any problems in the 4 years that I have been doing that. I must say that I use the fuel from the better filling stations that have very little ethonol in it and am very picky about the gas that I purchase.
 

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1992 Sedan DeVille
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821 Posts
Discussion Starter · #4 ·
Thanks, I'm going to be putting in 87 Octane from now on until gas prices go down. Just wanted to make sure I won't damage anything with the car by running regular. I've used 91 Oct previously but I just can't afford it anymore to run 91.
 

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2010 DTS
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88,476 Posts
Yea gas is crazy now, but your engine has no knock sensor so it cant adjust the timing to compensate, i tried once in mine it was knocking a little but the timing is also advanced a little
:yeah:

I drive my 92 deville 4.9 daily and use the regular gas all the time. I have not heard of any knock or have not had any problems in the 4 years that I have been doing that. I must say that I use the fuel from the better filling stations that have very little ethonol in it and am very picky about the gas that I purchase.
Ethanol actually raises the octane.

Thanks, I'm going to be putting in 87 Octane from now on until gas prices go down. Just wanted to make sure I won't damage anything with the car by running regular.
You won't damage anything unless you run it for a looong time with a sever knock and ignore it. Give it a shot and see if the engine will tolerate it. If it knocks, step up a grade and see if it likes that.
 

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1990 Deville w/ 250,000 mi
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280 Posts
There is a procedure to retard the timing to run the engine on regular. I believe it was a TSB. like for cars sold in other countries where premium is not available. Mine will knock on regular. I was just thinking about this today as I put in $25 bucks worth and only got 7 gallons.

Sorry for the hit and run.. I will update with the info probably later tonight.
 

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1992 Sedan DeVille
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821 Posts
Discussion Starter · #7 ·
There is a procedure to retard the timing to run the engine on regular. I believe it was a TSB. like for cars sold in other countries where premium is not available. Mine will knock on regular. I was just thinking about this today as I put in $25 bucks worth and only got 7 gallons.

Sorry for the hit and run.. I will update with the info probably later tonight.
No problem, thanks for the input.
 

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2011 Crown Vic LX, 2009 Chevy Malibu 2LT
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5,607 Posts
Texan is correct. If you really want to run regular, it's as simple as retarding the base timing a degree or two.
 

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1990 Deville w/ 250,000 mi
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280 Posts
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.
IGNITION TIMING ADJUSTMENT
Refer to the Vehicle Emission Control Information Label located in the engine compartment. Follow all instructions on the label.

PROCEDURE

1. With the ignition "OFF," connect the pick-up lead of the timing light to the number one spark plug. Use a jumper lead between the wire and plug, or an inductive type pick-up. DO NOT pierce the wire, or attempt to insert a wire between the boot and spark plug.
2. Connect the timing light power leads according to the manufacturers instructions.
3. Jumper pins A and B at the Assembly Line Diagnostic Link (ALDL) connector while NOT in diagnostic mode.
4. START the engine and aim the timing light at the timing mark. The line on the pulley should line up at the timing mark. If a change is necessary, loosen the distributor hold-down clamp bolt at the base of the distributor. While observing the mark with the timing light, slightly rotate the distributor until the line indicates the correct timing. Tighten the hold down bolt to 34 Nm (25 lb ft) and recheck the timing.
5. Turn "OFF" the engine. Remove timing light and jumper at the ALDL connector.
6. Reconnect number one spark plug wire, if removed.
 
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