FUELER Posted March 25, 2009 Share Posted March 25, 2009 Would there be a difference between 4.3's and 4.6's? gearing difference.... the 4.6's will turnn tires easier so slightly less load on the engine Link to comment Share on other sites More sharing options...
FUELER Posted March 25, 2009 Share Posted March 25, 2009 and i use 87 octane, sometimes 89 but really it makes no difference Link to comment Share on other sites More sharing options...
tekazgtr1984 Posted March 25, 2009 Share Posted March 25, 2009 gearing difference.... the 4.6's will turnn tires easier so slightly less load on the engine Giggity! Thanks for the info! Link to comment Share on other sites More sharing options...
fleurys Posted March 25, 2009 Share Posted March 25, 2009 I use 89 and saw a clear difference with fuel consumption compared to 92 or 94... I do more miles/gallon with the 89 octane. Link to comment Share on other sites More sharing options...
ben0326 Posted March 25, 2009 Share Posted March 25, 2009 89 octane. usually shell or BP Link to comment Share on other sites More sharing options...
colinnwn Posted March 26, 2009 Share Posted March 26, 2009 (edited) I do more miles/gallon with the 89 octane. You know I've been thinking about why this would be the case. Octane is a chemical, and the octane number of gas tells you the resistance to preignition of the gas in equivalent percentage of octane with the remaining amount heptane. So 89 octane gas has the preignition equivalent of 89% octane and 11% heptane. But gas companies make no guarantees about the actual chemical makeup of the gas, heat content, or density of the fuel. Ethanol just happens to have an AKI octane rating of 116, and a lower heat content than most other constituents of gasoline (that is the reason you get worse mileage with it). Ethanol is allowed in gas as an oxygenate, up to 10% without specifically noting the percentage. And ethanol prices have come down from their temporary sky high prices. Refiners may be using ethanol as the octane boosting product in premium gasoline. If this is the case, it means the premium fuel has a lower heat content, and will therefore give you fewer miles to the gallon, than regular gas. Edited March 26, 2009 by colinnwn Link to comment Share on other sites More sharing options...
FUELER Posted March 26, 2009 Share Posted March 26, 2009 Refiners may be using ethanol as the octane boosting product in premium gasoline. If this is the case, it means the premium fuel has a lower heat content, and will therefore give you fewer miles to the gallon, than regular gas. Did you hear about the proposed increase in ethanol % ? http://www.nytimes.com/2009/03/07/business...hanol.html?_r=1 Link to comment Share on other sites More sharing options...
SixGuns Posted March 26, 2009 Share Posted March 26, 2009 colinnwn, you go 20k miles on an oil change? Dude....just 'cause it's synthetic doesn't make it super oil. I'll run 6k on Penzoil Platnum 10w-30. But even then, man..at 6k, it's READY to be changed. Link to comment Share on other sites More sharing options...
OfftourRoadie96 Posted March 26, 2009 Author Share Posted March 26, 2009 Are there any special steps when making the switch to Synthetic Oil??? Also, TC, Front and Rear Diff??? Or do you just drain out the Regular and replace with the Synthetic? Link to comment Share on other sites More sharing options...
02silverpathy Posted March 26, 2009 Share Posted March 26, 2009 Did you hear about the proposed increase in ethanol % ? http://www.nytimes.com/2009/03/07/business...hanol.html?_r=1 Well, now corn will be over $5 for 12 ears and cans of corn will be $2! Lol, why not ask the public if they feel like doing extra maint. on their vehicles as this product saves environment marginally but affects your vehicles ability to run correctly greatly....this almost sounds like a poor offset. Or well at least they will be forcing us to do some maint as parts break down quicker. For the Octane topic: I say lets all add Toluene to our tanks and call it a day! Link to comment Share on other sites More sharing options...
colinnwn Posted March 26, 2009 Share Posted March 26, 2009 colinnwn, you go 20k miles on an oil change? Dude....just 'cause it's synthetic doesn't make it super oil. I'll run 6k on Penzoil Platnum 10w-30. But even then, man..at 6k, it's READY to be changed. The 3k "recommendation" was more necessary before high quality oils starting in the 70's were developed with better detergents, ph buffers, and rust inhibitors. Quick lube places have continued to perpetrate this myth in modern times of cleaner engines, better oils, and extended manufacturer oil change cycles. Engines used to run a lot dirtier, and wash a lot more unburnt hydrocarbons and coked carbons into the crankcase. Many auto manufacturers recommend extended oil changes on even dyno lube. I believe my Nissan Maxima the factory recommendation that carries the full force of warranty is oil changes every 8,750 miles, and filter changes at 17,500. Just because an oil looks dirty doesn't mean it isn't doing its job and needs to be replaced. I started doing 20k oil changes on my Maxima (which runs great at over 300k miles) because I read about how many trucking companies do 1,000,000 mile oil changes. Granted they usually do an oil analysis every couple months, some run a secondary low micron filter, and a few even run oil decanters to burn off any volatiles in the oil. They sometimes put an additive package into the oil when the ph is getting high. But I think 20k miles on synthetic without taking all these precautions is fairly conservative. If I did all the things big trucking companies do, I'd never change my oil unless the oil analysis indicated it was time. Did you hear about the proposed increase in ethanol % ? I did hear about it and I think it is BS unless they can prove a case that additional oxygenates are needed in gas for improved emissions. There have been enough studies that ethanol from corn is a net cost to the environment in land degradation, water use, and energy loss in conversion from corn to ethanol. Now if they can get switchgrass ethanol working, maybe it isn't as big a deal. Cars built since 2000 are more resistant to water in gas (the first major drawback of ethanol because it is hydrophillic and tends to rust internal fuel system parts), and they have ethanol resistant rubber components (because rubber from older cars disintegrates in ethanol). However, you don't put food products in the tank of your car. The spike in corn prices from the beginning of ethanol use as an oxygenate caused millions of people in the world to go hungry and probably killed thousands, if not hundreds of thousands of people. Are there any special steps when making the switch to Synthetic Oil??? If your car is in good shape, then no I didn't do anything and I have had no problems. However if you have an old car where the seals are worn out and are only holding because of dyno oil sludge, then your car may start acting like an oil sieve. Synthetic is a very good detergent and can work its way around compromised seals. The only other precaution is if you go synthetic, don't go back to dyno. Everything I have heard is doing that is hard on your engine. Link to comment Share on other sites More sharing options...
tekazgtr1984 Posted March 26, 2009 Share Posted March 26, 2009 Yup, definitely stay synthetic should you make the change. So changing my oil every 3,000 miles is pretty much pointless? I'm running Castrol Syntec 5W30 and am doing oil changes at intervals between 3-4k based on my old man's advice. After reading up on this thread, it sounds like I could probably stretch it out to 5-6k or even higher. I'm also wondering, does weather play a factor here? Where I live, the seasons differ greatly. Naturally, this puts more stress on a vehicle so perhaps more frequent oil changes would benefit the life of the vehicle. In the first 11 months since picking up my R50, I've only put about 10,000km (6,000 miles). Essentially, I'm only doing two oil changes over a 12 month period. That seems average but the mileage I've put on is way below the norm... For what it's worth, I guess just sticking to 6 month intervals is ideal... Link to comment Share on other sites More sharing options...
arcano Posted March 26, 2009 Share Posted March 26, 2009 I did a lot of research on the topic of fuel octane a long time ago. My understanding from multiple sources is that the difference between low and high octane fuel is ONLY that the higher octane fuel has a higher resistance to spontanous ignition, which is good on engines with higher compresion to prevent knocking. In other words, higher octane fuel packs the same puch (energy per gallon) but requires more heat/pressure/spark to burn completly. In a high-compression engine, the high octane fuel will burn completly due to the additional pressure and temperature in the combustion chamber. BUT, in a lower compression engine that is not designed for it, the high octane fuel will not always burn completly, so you will get less energy out of each gallon of fuel, and thus lower mileage. So: Engine with high compression + higher octane fuel = higher mileage and no knocking Engine with high compression + lower octane fuel = lower mileage due to knocking Engine with lower compression + lower octane fuel = higher mileage due to more efficient burning (as long as some other problem is not causing knocking) Engine with lower compression + higher octane fuel = lower mileage due to incomplete burning (but may fix knocking problems) I hope it makes sense... Link to comment Share on other sites More sharing options...
laxman0324 Posted March 26, 2009 Share Posted March 26, 2009 I did a lot of research on the topic of fuel octane a long time ago. My understanding from multiple sources is that the difference between low and high octane fuel is ONLY that the higher octane fuel has a higher resistance to spontanous ignition, which is good on engines with higher compresion to prevent knocking. In other words, higher octane fuel packs the same puch (energy per gallon) but requires more heat/pressure/spark to burn completly. In a high-compression engine, the high octane fuel will burn completly due to the additional pressure and temperature in the combustion chamber. BUT, in a lower compression engine that is not designed for it, the high octane fuel will not always burn completly, so you will get less energy out of each gallon of fuel, and thus lower mileage. So: Engine with high compression + higher octane fuel = higher mileage and no knocking Engine with high compression + lower octane fuel = lower mileage due to knocking Engine with lower compression + lower octane fuel = higher mileage due to more efficient burning (as long as some other problem is not causing knocking) Engine with lower compression + higher octane fuel = lower mileage due to incomplete burning (but may fix knocking problems) I hope it makes sense... I agree with all of this except the bolded statement. I think that statement is true everywhere except for on the highway. I have heard and had experience with my ML that it got better mileage with lower octane on the highway. As I said before I think that the lower octane fuel is easier for the high compression engine to burn on the highway...just my guess but I do know that lower octane fuel yields higher mileage on the highway... Link to comment Share on other sites More sharing options...
colinnwn Posted March 26, 2009 Share Posted March 26, 2009 As I said before I think that the lower octane fuel is easier for the high compression engine to burn on the highway... You haven't really said anything here that can be quantified. What is easier burning? Burns faster, burns more completely, why is it happening? Absent more evidence, I think the reasonable explanation is today, (which might be different than in the past, and it may even vary from season to season now as they change the gas mixture for emissions and summer ozone), the heating value of regular gas is higher than the heating value of high octane gas. Link to comment Share on other sites More sharing options...
laxman0324 Posted March 26, 2009 Share Posted March 26, 2009 You haven't really said anything here that can be quantified. What is easier burning? Burns faster, burns more completely, why is it happening? Absent more evidence, I think the reasonable explanation is today, (which might be different than in the past, and it may even vary from season to season now as they change the gas mixture for emissions and summer ozone), the heating value of regular gas is higher than the heating value of high octane gas. I thought I said I didn't have any techincal reasons in one of my posts, but it is simply speculation because I have found the mileage increase with regular on the highway in high compression engines to be true.. Link to comment Share on other sites More sharing options...
tekazgtr1984 Posted March 26, 2009 Share Posted March 26, 2009 Weather and short trips can play a factor because rapid temp fluctuations allow condensation to build up in the oil, and short trips don't give the engine enough time to heat up and fully dry out the oil. But changing oil more frequently won't really help, unless you change it after every trip. Even if you drive the truck infrequently, the more important thing is to run it long enough the engine fully warms up and vaporizes all the condensation in the oil. 6 month interval is great as long as you don't mind the time and expense to change your oil. Thanks for clarifying that for me. I had a feeling weather played but the short trip issue never really crossed my mind. Luckily, I make sure when I take short trips, especially in colder months, I allow the engine ample time to warm up and eliminate any condensation accumulation. To get back to this issue of octane/compression/mileage/etc., based on my own experience, my mileage has appeared to have improved on account of using 91 octane fuel. Especially on the highway, my R50 sips. My friend with a same year R50 gets worse mileage than I do running 87... Granted he's got 4.3's; I've got 4.6's and 32's... Overall, running 91 octane has been beneficial in my case. Link to comment Share on other sites More sharing options...
ronin152 Posted March 27, 2009 Share Posted March 27, 2009 I use 89 in mine and put 93 when I have alot of gas points. The engine does "seem" to run smoother with the 93 sounds alot better. I remember in a v8 audi we had that when you would put anything less than 93 it would sound and run like crap. Link to comment Share on other sites More sharing options...
Fukinitupagain Posted March 27, 2009 Share Posted March 27, 2009 You are having pre-ignition, and you want to stop it. Your engine is a VG, so it should be perfectly happy on 89 or even 87. If it happens regularly (not just when you occasionally jump on it at low engine speed), you have 2 choices. If 91 always fixes it, then use it. Or you can try to find the root cause. I noticed you are running 32 inch tires. The larger tire means there is more load on your engine unless you switched your differential ratio to make up for it. That could be a contributing factor. If you live in a high elevation, or especially hot area that would make it worse. If you have a manual and you tend to run the highest gear you can, without downshifting to accelerate, that could cause it. You could also have a bad knock sensor, or MAF sensor, or maybe clogged injectors. I'm running 4.6's the tires turn fine, I don't live in a higher elevation & I'm in the South but not the Deep South, so its not too hot. I have an auto tranny, the injectors are clean & MAF sensor is good. Maybe its the knock sensor but you know I had this issue with the original engine as well... oh well. Link to comment Share on other sites More sharing options...
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