Babydon Posted June 3, 2008 Report Share Posted June 3, 2008 With gas prices rising like a tsunami, how beneficial is it to pump 94 octane over the lowest grade gasoline? Link to comment Share on other sites More sharing options...
KenD Posted June 3, 2008 Report Share Posted June 3, 2008 i've been running regular gas for the last year and a half and have seen no difference. Ken 1994 STS Pearl White 260,000 KM (163,000 miles) <img src="http://img45.photobucket.com/albums/v137/caesar/caddycaesar.jpg" border="0" class="linked-sig-image" /> Link to comment Share on other sites More sharing options...
littleoletot Posted June 4, 2008 Report Share Posted June 4, 2008 My 2001 STS runs fine on regular unleaded but after trying only premium for 1500 miles I am getting an extra 3.5 M.P.G. , and it performs noticeably better so swings and roundabouts I guess ! Link to comment Share on other sites More sharing options...
JasonA Posted June 5, 2008 Report Share Posted June 5, 2008 My '01 STS gets better mileage on premium as well. It's not 3.5 MPG, but it's enough to make the cost/mile about equivalent. But that was with the cheaper gas, and with the price difference between regular and premium only 20 cents. Now that some stations are selling premium for 30+ cents more than regular, my cost/mile is higher. But the car still has better performance on premium, especially in the summer time. My '97 SLS didn't care for regular fuel at all. There were noticeable driveability problems, and some spark knock. My '01 runs fine on it...just not as "snappy". Jason(2001 STS, White Diamond) "When you turn your car on...does it return the favor?" Link to comment Share on other sites More sharing options...
thaghost87 Posted June 5, 2008 Report Share Posted June 5, 2008 My '01 STS gets better mileage on premium as well. It's not 3.5 MPG, but it's enough to make the cost/mile about equivalent. But that was with the cheaper gas, and with the price difference between regular and premium only 20 cents. Now that some stations are selling premium for 30+ cents more than regular, my cost/mile is higher. But the car still has better performance on premium, especially in the summer time. My '97 SLS didn't care for regular fuel at all. There were noticeable driveability problems, and some spark knock. My '01 runs fine on it...just not as "snappy". are the 00-01 sts's built for premium? i saw BBF talking about a carbon build up factor in some vehicles if their engines arent built for a premium gas... i use premium and not wonder about the carbon thing... Link to comment Share on other sites More sharing options...
Texas Jim Posted June 5, 2008 Report Share Posted June 5, 2008 My '01 STS gets better mileage on premium as well. It's not 3.5 MPG, but it's enough to make the cost/mile about equivalent. But that was with the cheaper gas, and with the price difference between regular and premium only 20 cents. Now that some stations are selling premium for 30+ cents more than regular, my cost/mile is higher. But the car still has better performance on premium, especially in the summer time. JasonA, At over $4 bucks for Premium, NOW and at $3 bucks for premium THEN...it is still the same PERCENTAGE difference. A few more actual cents out of your POCKET, but still the same percentage. And when you find a station that is LESS then 30 cents difference... it is actually a SMALLER percentage than it used to be. Link to comment Share on other sites More sharing options...
JasonA Posted June 5, 2008 Report Share Posted June 5, 2008 are the 00-01 sts's built for premium? i saw BBF talking about a carbon build up factor in some vehicles if their engines arent built for a premium gas... i use premium and not wonder about the carbon thing... Officially, the Cadillac owner's manual says 87 is fine for regular use, and is the recommended grade. It also says, however, that higher levels of performance may be found with premium fuel. The Northstar was originally designed on premium fuel. 91 octane was printed in the owner's manuals and the fuel gauge said "PREMIUM UNLEADED ONLY". In 2000, the Northstar was redesigned a bit, and the combustion chambers were re-shaped and the compression ratio lowered slightly, etc. The owner's manuals were updated to show 87 octane as the minimum octane rating, and the premium fuel requirement was removed from the gas gauge. It's still largely the same engine, though, and most people's engines do run better on premium, and there's still apparently some spark timing retard when running 87 octane. What BodyByFisher posted is often applied to older engines, though it probably does apply somewhat to Northstars as well. Take, for instance, my wife's 2007 Chrysler Town & Country, or my other car, a '97 Dodge Dakota. Both of these vehicles use older engine designs, with cam-in-block (pushrod) construction, and have lower compression ratios. The Dakota (5.2L V-8) doesn't even have a knock sensor I don't think; I'm not sure about the 3.8L V-6 in the van, whether it has a knock sensor or not. Both of these engines, with their relatively low compression ratios (about 9:1 in both I think) are clearly designed to be used only on regular octane fuel. Dodge has even issued a TSB that echos what BodyByFisher posted earlier; that is, using a fuel with an octane rating higher than necessary promotes increased deposit formation and increased driveability issues. When it gets down to it, I really think the deposit issue is mostly moot with our engines -- regardless of if you have a pre-2000 Northstar or a newer one, or if you have the 275-hp version or the 300-hp version, all are relatively modern engines with tight tolerances and high compression ratios. Because Cadillac either recommends (for older engines) or acknowledges the benefits of (for newer engines) premium fuel, I see no danger in using whatever grade you like, as long as you like how the car runs. Jason(2001 STS, White Diamond) "When you turn your car on...does it return the favor?" Link to comment Share on other sites More sharing options...
JasonA Posted June 5, 2008 Report Share Posted June 5, 2008 A few more actual cents out of your POCKET, but still the same percentage. And when you find a station that is LESS then 30 cents difference... it is actually a SMALLER percentage than it used to be. Jim, you are correct. I do look for those stations that still sell the three grades 10 cents apart. And you are right -- when you do the math -- it still comes out the same. All it takes is a ~1 MPG gain to make the difference worth it. Jason(2001 STS, White Diamond) "When you turn your car on...does it return the favor?" Link to comment Share on other sites More sharing options...
thaghost87 Posted June 5, 2008 Report Share Posted June 5, 2008 are the 00-01 sts's built for premium? i saw BBF talking about a carbon build up factor in some vehicles if their engines arent built for a premium gas... i use premium and not wonder about the carbon thing... Officially, the Cadillac owner's manual says 87 is fine for regular use, and is the recommended grade. It also says, however, that higher levels of performance may be found with premium fuel. The Northstar was originally designed on premium fuel. 91 octane was printed in the owner's manuals and the fuel gauge said "PREMIUM UNLEADED ONLY". In 2000, the Northstar was redesigned a bit, and the combustion chambers were re-shaped and the compression ratio lowered slightly, etc. The owner's manuals were updated to show 87 octane as the minimum octane rating, and the premium fuel requirement was removed from the gas gauge. It's still largely the same engine, though, and most people's engines do run better on premium, and there's still apparently some spark timing retard when running 87 octane. What BodyByFisher posted is often applied to older engines, though it probably does apply somewhat to Northstars as well. Take, for instance, my wife's 2007 Chrysler Town & Country, or my other car, a '97 Dodge Dakota. Both of these vehicles use older engine designs, with cam-in-block (pushrod) construction, and have lower compression ratios. The Dakota (5.2L V-8) doesn't even have a knock sensor I don't think; I'm not sure about the 3.8L V-6 in the van, whether it has a knock sensor or not. Both of these engines, with their relatively low compression ratios (about 9:1 in both I think) are clearly designed to be used only on regular octane fuel. Dodge has even issued a TSB that echos what BodyByFisher posted earlier; that is, using a fuel with an octane rating higher than necessary promotes increased deposit formation and increased driveability issues. When it gets down to it, I really think the deposit issue is mostly moot with our engines -- regardless of if you have a pre-2000 Northstar or a newer one, or if you have the 275-hp version or the 300-hp version, all are relatively modern engines with tight tolerances and high compression ratios. Because Cadillac either recommends (for older engines) or acknowledges the benefits of (for newer engines) premium fuel, I see no danger in using whatever grade you like, as long as you like how the car runs. thanks Jason for clearing that up for me.. i do run premium, and i dont know if its me or not, but it does seem to get better mpg on premium.. i just didnt wanna hurt my engine.. how often should WOT's be performed? Link to comment Share on other sites More sharing options...
JasonA Posted June 5, 2008 Report Share Posted June 5, 2008 thanks Jason for clearing that up for me.. i do run premium, and i dont know if its me or not, but it does seem to get better mpg on premium.. i just didnt wanna hurt my engine.. how often should WOT's be performed? Running premium isn't going to hurt the engine...just like it's not "better" for the engine nor will it make it last longer. It simply has less of a tendency to knock, so the spark advance can be safely increased. I let the engine run up to redline at least once a day. It really is true that the harder you drive these engines, the better they seem to run. Jason(2001 STS, White Diamond) "When you turn your car on...does it return the favor?" Link to comment Share on other sites More sharing options...
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