scott y Posted April 29, 2011 Report Share Posted April 29, 2011 Now that the Price/L for premium fuel is quickly closing in on the $1.60 area,here in Ontario,I think that we're going to start experimenting. First with 89 grade and slowly wean down to 87. On the wife's 02 STS it should have little to no effect, however on the 94 STS that kind of has me wondering. I have been doing some online research about knock sensors and so forth, and found a very interesting article by Beezlebob in the other forum, that was very clear about the use of regular gas in all Northstar engines. Well worth reading if any one else is concerned. Link to comment Share on other sites More sharing options...
BodybyFisher Posted April 29, 2011 Report Share Posted April 29, 2011 Can you provide the link Beezlebob? I am curious what he said, if I recall, I think he would say that using 87 in a car that requires premium retards the ignition and that you would get better fuel economy with premium and you are not really saving any money using regular. Pre-1995 - DTC codes OBD1 >> 1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/ Cadillac History & Specifications Year by Year http://www.motorera.com/cadillac/index.htm Link to comment Share on other sites More sharing options...
scott y Posted April 29, 2011 Author Report Share Posted April 29, 2011 Hi there Mike, in post #21 you will see Beezlebob's input, http://www.cadillacforums.com/forums/cadillac-seville-cadillac-eldorado-forum/7104-how-important-using-premium-gas-94-a.html Keeping in mind that this was from 2004...Quick question, is this "The Guru"? Link to comment Share on other sites More sharing options...
Göran W Posted April 29, 2011 Report Share Posted April 29, 2011 Hmmmmm...... In Sweden there is NO fuel under 95 octane and still the same question..... Will the low octane (95) do damage to my engine? Link to comment Share on other sites More sharing options...
scott y Posted April 29, 2011 Author Report Share Posted April 29, 2011 Goran, read my link in Post#3 Link to comment Share on other sites More sharing options...
cdgrinci Posted April 29, 2011 Report Share Posted April 29, 2011 Hmmmmm...... In Sweden there is NO fuel under 95 octane and still the same question..... Will the low octane (95) do damage to my engine? In Europe octane is rated as RON (research octane), in the U.S., octane is rated by averaging RON and Motor Octane; this octane number is lower than the European posted number. What you need to consider is what is recommended for your vehicle (see your owner's manual) and determine whether you need base octane or a higher octane (commonly called regular and premium here). Chuck '19 CT6, '04 Bravada........but still lusting for that '69 Z-28 Link to comment Share on other sites More sharing options...
Ranger Posted April 30, 2011 Report Share Posted April 30, 2011 Hi there Mike, in post #21 you will see Beezlebob's input, http://www.cadillacforums.com/forums/cadillac-seville-cadillac-eldorado-forum/7104-how-important-using-premium-gas-94-a.html Keeping in mind that this was from 2004...Quick question, is this "The Guru"? Scott, Yes you can burn regular and yes, that was "the Guru". Link to comment Share on other sites More sharing options...
Göran W Posted April 30, 2011 Report Share Posted April 30, 2011 Ooops, learned somthing new! Thanks!! Link to comment Share on other sites More sharing options...
mike5514 Posted April 30, 2011 Report Share Posted April 30, 2011 Good!!! made my day. Mike Link to comment Share on other sites More sharing options...
Göran W Posted April 30, 2011 Report Share Posted April 30, 2011 Studying the text from "Beelzebob" was very useful, especially since I own a ESC 2000! Link to comment Share on other sites More sharing options...
BodybyFisher Posted April 30, 2011 Report Share Posted April 30, 2011 Yes you can use it, but you should do a test before you do. Run with a tank of 91 and check your MPG then run with a tank of 89 and check your MPG, that is a VERY important key bit of information. As you know, the Northstar has a knock sensor, putting 87 in an engine that favors 91 will cause a knock. A knock is caused because there is insufficient octane and the fuel mixture detonates prematurely from the heat and pressure. (I hate when that happens).. Anyway, detonation can do mechanical damage and the PCM knows that because it hears the knock via the knock sensors and it retards the ignition as needed to stop the knocking and save the engine. In the "de-tuning" process, the engine looses power and efficiency and the Miles Per Gallon DROP. IF the drop is only 1 mile per gallon, say a drop from 15 miles per gallon down to 14 miles per gallon, the SO CALLED savings that you THINK you are getting ends up being MINIMAL and for that SO CALLED big savings you are degrading your performance. In the following example I fill up with 20 gallons of fuel. I just checked www.gasbuddy.com and at my local station REGULAR is $4.15 per gallon and PREMIUM is $4.37. This is not an easy decision nor is it clear cut that using REGULAR is cheaper. There are a few variables that must be considered. In addition, as the summer gets HOTTER, the PCM will need to further retard the timing. The hotter the engine the more apt it will be for it to detonate with regular and further require detuning. So in my humble opinion where you live also must be factored into this decision, but that will become evident when you run the test to measure the difference in MPG between REGULAR and PREMIUM is done. The following things must be considered and have an impact on the results affecting your decision. A simple Excel spreadsheet can be built that can easily analyze the variables. It is interesting to note that doing HIGHWAY driving the cost of the trip getting 24 vs 23 using PREMIUM costs you more for the trip as compared to CITY driving where PREMIUM saves you money for the trip: 1) The MPG LOST using REGULAR vs PREMIUM 2) The price differential between REGULAR and PREMIUM 3) The type of driving being done Pre-1995 - DTC codes OBD1 >> 1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/ Cadillac History & Specifications Year by Year http://www.motorera.com/cadillac/index.htm Link to comment Share on other sites More sharing options...
hot rod Posted May 1, 2011 Report Share Posted May 1, 2011 I haven't checked the mileage on my 96 but I will say it seems to burn less gas on premium than the mid grade. I will have to compare. It runs better on premium.I can feel it. Gas prices are ridiculous in Chicago.Gone are the days when I would cash in the soda bottles and fill up my dirt bike. Link to comment Share on other sites More sharing options...
Texas Jim Posted May 2, 2011 Report Share Posted May 2, 2011 For what it might be worth...or not... My owners manual RECOMMENDS Premium...but says you can use regular... if you have to. I did a lot of testing of Regular vs Premium in my car the first year I had it... back in 2006. I ran various grades in it for most of 20,000 miles. What I found was.... it took almost a 10 percent hit on fuel mileage... and a noticeable drop in performance. Since I probably drive a little harder and faster than MOST Cadillac drivers, the performance drop concerned me. Since the price difference is LESS than a 10 percent difference in regular and Premium... I switched back to Premium For "ME" the price is almost EXACTLY the same PER MILE driven.. and actually might be a tiny bit cheaper using Premium, because it gets better mileage. Plus, I don't take the big performance hit. Of course cars vary and your results may very well be different than mine... Just thought I would throw out my experience for what it may be worth to someone. Link to comment Share on other sites More sharing options...
BodybyFisher Posted May 2, 2011 Report Share Posted May 2, 2011 That is great Jim, you supported the premise in what I was saying above. That using regular causes both a performance hit and a fuel mileage hit. So at an average MPG of 14 that equates to a drop of 1.4 to 12.6 MPG, and at an average MPG of 24 that equates to a drop of 2.4 or 21.6 MPG. Interesting. I just looked at my charts above and I think I have a logic error in them and I need to rethink them maybe the board can help me here. The problem with my thinking is that I compared apples to oranges by comparing the COST DIFFERENCE of buying 20 gallons of fuel, to the FUEL USED in a 250 mile trip that is an arbitrary analysis. I have only had one cup of coffee and my brain is still in OPEN LOOP, but there must be a good way to show this comparison in dollar terms Any ideas on mathematically showing the difference? I think it can been done simply by tallying how far a full tank would take you and looking at it on a cost per mile basis... any ideas? Thanks Jim Pre-1995 - DTC codes OBD1 >> 1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/ Cadillac History & Specifications Year by Year http://www.motorera.com/cadillac/index.htm Link to comment Share on other sites More sharing options...
Texas Jim Posted May 2, 2011 Report Share Posted May 2, 2011 That's the way I figured mine.... How many gallons did I use going 1000 miles on regular. How many gallons did I use going 1000 miles on Premium. It tales more gallons when I use regular. So.... when I have to buy more GALLONS... to go the same distance... I am not saving any money. And that is not even considering that it doesn't run as well on Regular as it does on Premium. Link to comment Share on other sites More sharing options...
BodybyFisher Posted May 2, 2011 Report Share Posted May 2, 2011 Ok good Jim with that thought in mind I put this together, does this make sense to you? So the moral to this story is never assume that going cheap is better even though on the surface it appears so. Pre-1995 - DTC codes OBD1 >> 1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/ Cadillac History & Specifications Year by Year http://www.motorera.com/cadillac/index.htm Link to comment Share on other sites More sharing options...
Texas Jim Posted May 3, 2011 Report Share Posted May 3, 2011 Ok good Jim with that thought in mind I put this together, does this make sense to you? So the moral to this story is never assume that going cheap is better even though on the surface it appears so. That is absolutely correct... You wouldn't believe how many times I have tried to explain that to people and they just look at you like you were from Mars or something... :) All they can say is...but it costs less to buy regular... and CAN NOT reason thru the issue... Link to comment Share on other sites More sharing options...
mike5514 Posted May 3, 2011 Report Share Posted May 3, 2011 bbf nice! I used your figures but changed the avg. reg. mpg. to 21 and my savings were 1.13 a tank I use a tank every couple of weeks. (Dont drive much any more). But if i were commuting I might be using a tank or 2 every wk. in either case its enough to buy oil and a filter for my baby plus a 6pk of millers for me and some quality time in the garage. Mike Link to comment Share on other sites More sharing options...
BodybyFisher Posted May 3, 2011 Report Share Posted May 3, 2011 Jim, that is because they don't understand how the PCM works to eliminate knocking and furthermore they don't understand how much impact retarding the ignition has on fuel mileage and performance. Like you, I have tried to explain this issue to people and they just don't get it. They have cars that call for Premium but they put the cheapest low octane fuel in that they can buy, saying it does not make a difference, when it does. Everytime the fuel goes through the roof, we get members here asking if they can use regular. Well yes you can, BUT....at what cost? I do know one thing, I was unable/unwilling to use regular in the hot months as I would get a loud knocking when I pulled away from a stop. Yes the knock sensor eliminated it by retarding the timing sufficiently but again at WHAT COST of performance and EFFICIENCY. Anyone who is considering using REGULAR 87 needs to run tests, driving similar courses (commuting, highway driving, etc) to see the impact. If anyone wants this EXCEL spreadsheet, PM me an email address and let me know what version of EXCEL you have, I have it saved in EXCEL 2007 format Pre-1995 - DTC codes OBD1 >> 1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/ Cadillac History & Specifications Year by Year http://www.motorera.com/cadillac/index.htm Link to comment Share on other sites More sharing options...
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