Miked2009 Posted August 10, 2010 Report Share Posted August 10, 2010 Hey everyone really quick question I know it says to use premium gas but today i mixed 93 premium and 89 I was wondering if I can just use 89 with the mix there is no knocking or pinging I just wanted some opinions because I seen a lot of people use 89 or 87 in there devilles with no problems. Thanks Mike Link to comment Share on other sites More sharing options...
Texas Jim Posted August 10, 2010 Report Share Posted August 10, 2010 You will get answers from both sides on "THAT" question... :D I have always believed that since Cadillac spent the money "VALIDATING" what fuel it needs for optimal operation...I always use what they recommend. I have tried regular a few times .. just for grins ... to see what it would do. I get no pinging, but it doesn't run quite as well and it gets slightly "LESS" fuel mileage. When you figure the extra fuel it burns using regular... there is no cost saving to it. Mine calls for Premium...therefore nothing but Premium goes into it. And that's "MY" opinion and I am sticking to it... Link to comment Share on other sites More sharing options...
Miked2009 Posted August 10, 2010 Author Report Share Posted August 10, 2010 You will get answers from both sides on "THAT" question... :D I have always believed that since Cadillac spent the money "VALIDATING" what fuel it needs for optimal operation...I always use what they recommend. I have tried regular a few times .. just for grins ... to see what it would do. I get no pinging, but it doesn't run quite as well and it gets slightly "LESS" fuel mileage. When you figure the extra fuel it burns using regular... there is no cost saving to it. Mine calls for Premium...therefore nothing but Premium goes into it. And that's "MY" opinion and I am sticking to it... ok im going with u im sticking with premium thats what ive used the last year and 3 months since i bought the car so thats what im gonna keep using i cleaned out the throttle body bores today much smoother idle still got a lot more work to it Link to comment Share on other sites More sharing options...
Ranger Posted August 11, 2010 Report Share Posted August 11, 2010 If it was a Northstar you could do it. It has a very effective knock sensor and will adjust the timing to compensate if it detects a spark knock. The 4.9 unfortunately does not have a knock sensor so you are pretty much stuck with premium. Won't hurt to experiment though if you are so inclined. Link to comment Share on other sites More sharing options...
KHE Posted August 11, 2010 Report Share Posted August 11, 2010 When the tank gets close to empty, fill it to the half-way point with 89 octane and drive it. If it doesn't ping and you're OK with the fuel economy, then you can run 89 octane fuel. If it pings, you can just fill the tank the rest of the way with Premium. The other option is to retard the timing if it pings on the lower octane fuel but that will affect performance and fuel economy. Kevin '93 Fleetwood Brougham '05 Deville '04 Deville 2013 Silverado Z71 Link to comment Share on other sites More sharing options...
Miked2009 Posted August 11, 2010 Author Report Share Posted August 11, 2010 When the tank gets close to empty, fill it to the half-way point with 89 octane and drive it. If it doesn't ping and you're OK with the fuel economy, then you can run 89 octane fuel. If it pings, you can just fill the tank the rest of the way with Premium. The other option is to retard the timing if it pings on the lower octane fuel but that will affect performance and fuel economy. Ok thanks everyone how much less fuel economy will i get right now i am getting about 14.5MPG in the city and 23MPG highway Link to comment Share on other sites More sharing options...
Texas Jim Posted August 11, 2010 Report Share Posted August 11, 2010 When the tank gets close to empty, fill it to the half-way point with 89 octane and drive it. If it doesn't ping and you're OK with the fuel economy, then you can run 89 octane fuel. If it pings, you can just fill the tank the rest of the way with Premium. The other option is to retard the timing if it pings on the lower octane fuel but that will affect performance and fuel economy. Ok thanks everyone how much less fuel economy will i get right now i am getting about 14.5MPG in the city and 23MPG highway Mike, All cars are different of course and all I can speak for is "MY" car. The few times I tried running regular in mine... the mileage took a round a 10 percent hit. Plus the performance was also down enough that it was noticeable... at least to me. My mileage on the highway dropped from around 22 to about 20. Since there is only about 10 percent difference in the price of Regular and Premium... I really wasn't saving any money by running the lower octane fuel. Of course.. your car and your driving style may be totally different from mine, so it may benefit you a little bit. Link to comment Share on other sites More sharing options...
Miked2009 Posted August 11, 2010 Author Report Share Posted August 11, 2010 When the tank gets close to empty, fill it to the half-way point with 89 octane and drive it. If it doesn't ping and you're OK with the fuel economy, then you can run 89 octane fuel. If it pings, you can just fill the tank the rest of the way with Premium. The other option is to retard the timing if it pings on the lower octane fuel but that will affect performance and fuel economy. Ok thanks everyone how much less fuel economy will i get right now i am getting about 14.5MPG in the city and 23MPG highway Mike, ok thanks a lot All cars are different of course and all I can speak for is "MY" car. The few times I tried running regular in mine... the mileage took a round a 10 percent hit. Plus the performance was also down enough that it was noticeable... at least to me. My mileage on the highway dropped from around 22 to about 20. Since there is only about 10 percent difference in the price of Regular and Premium... I really wasn't saving any money by running the lower octane fuel. Of course.. your car and your driving style may be totally different from mine, so it may benefit you a little bit. Link to comment Share on other sites More sharing options...
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