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Synthetic Oils

Discussion in 'The Garage' started by Drey, Jul 31, 2006.

  1. Drey

    Drey 3/4 ton status

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    The other day some guys and me were bitching about the high gas prices and vehicle mileage. Another guy I work with who also drives a S10 blazer, pretty much the same as mine but a few years newer, said that he can get 23 MPG with it on the highway and around 18 in town. I on the other hand barely get 18 highway and 15 in town. Now Ive been babying it latly to save some gas and I still dont get much above that.



    He claims using synthetic oil in my motor will get me at least 3 MPG better. Am I right in thinking hes full of it, or is that in the realm of possibility. I assumed it just had to do with my blazer haveing 146000 miles on it and his having around 60000. His is a 99 or 2000 i believe mine is a 96. Both 4 door with 4.3 vortecs
     
  2. neverendingproject

    neverendingproject 1/2 ton status

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    Im thinking more like .3 MPG unless youre running a high weight oil.
     
  3. midnitewarya

    midnitewarya Sounds like a problem for future me. Premium Member

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    Never heard of that before. It might help, but I doubt it would be worth the cost. I run syntech, have been since it was new. I think it is the only reason my motor has lasted as long as it has. I get about 16 or so on the highway.
     
  4. Drey

    Drey 3/4 ton status

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    Motor calls for 5w-30

    I run 10w-30 its all my dad and I have ever run in our gas vehicles.

    Next oil change though I am getting the Oil for High Mileage engines per a reccomendation. My 4.3 has dropped oil pressure ever so slightly. But It buggin the hell out of me to have 55 PSI instead of the 60 I used to have:rolleyes:
     
  5. 4by4bygod

    4by4bygod 1/2 ton status

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    The oil for high mileage engines won't do much for your oil pressure problem.. they're designed to swell your seals and stop leaks, that's pretty much it. At some point though, the seals can't take any more and it leaks worse than before..

    As far as synthetics and mileage, you'll get a little bit, but how much depends on the vehicle.. there's no magic friction reducing element in the oil..all that's going on is that the petroleum molecules that make up the oil have been made to be the same size.. that's how you get the term "synthetic", and thus a bit less parasitic loss, easier starting, etc.

    what kind of shape is the engine in? If you really want mileage, use the 5w30.. if you don't see high rpm's, what can it hurt?

    Tom
     
  6. BigBen

    BigBen 1/2 ton status Premium Member

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    My experience is that most people have no idea what gas mileage they are actually getting.

    It's usually a guess, or they did some quick math once and that is what they remember.

    Unless you know that you are both consistently keeping a log of gallons to fill a tank and miles driven, you 'll never really know.

    Comparing gas mileage with most people is like discussing that fish that got a way.......



    BTW: I've been running Valvoline Max Life 10w-30 in my '95 Yukon since 110,000 miles (at 216,000 now) and I have no complaints, however, it didn't make any difference in my gas mileage, only oil consumption.
     
  7. goldwing2000

    goldwing2000 Guest

    And that's why you get worse mileage than your buddy. The engine was designed for 5W-30 but since you know better than the people who made it, you decided to go with 10W-30. :rolleyes:

    Thicker oil causes higher internal resistance, higher resistance means the engine is working harder, which uses more fuel.
     
  8. Pookster

    Pookster 1/2 ton status

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    that may work in theory, but in practice, that just isnt the case. Once your operating temp is up, the 10w30 and 5w30 dont have any noticible viscosity difference.
     
  9. goldwing2000

    goldwing2000 Guest

    That may be true but oil takes a lot longer to reach operating temp than coolant and while it's still warming up, you're listening to the nickels falling out the tail pipe.

    Of course... we have no idea how the vehicle is maintained, what accessories have been added, differences in tires, etc, etc, etc. Everything affects mileage.
     
  10. diesel4me

    diesel4me 1 ton status Premium Member

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    call me a sceptic but..

    I would rather run 10w-30 (or thicker!) in a vehicle,one that has some milage on it anyway,even if 5W-30 was reccomended..my theory is 5W-30 is great in cold weather,or light load conditions,or when the engine is new and "tight"..but its too thin to protect things when it gets up to 90+ degrees in the summer,and towing or other heavy use,I'd feel it would possible cause damage due to viscosity loss..it'll burn,even evaporate faster too..

    I'd rather lose 2-3 mpg from using thicker oil,than to lose the main and rod bearings because the oil thinned out too much for my high mileage engine with "loose" clearances,and it lost oil pressure...oil and gas is cheaper than engines!..

    I suspect synthetics DO give a BIT mor MPG..but they cost so much it isn't worth using it in an older engine..it'll leak and burn more oil than regular petroleum based oils,and some engines run on regular oil don't like being switched over to synthetic..I've seen a few blow up not long after the oil was changed..:crazy:
     
  11. goldwing2000

    goldwing2000 Guest

    He said he's been running 10W-30 since it was new.

    If you ever have doubts about the efficacy of your oil, have it sent in for analysis. That will tell you if you're wearing your engine out or not.
     
  12. Pookster

    Pookster 1/2 ton status

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    Depending on the brand of oil, you can find their CST values.

    Most 5w30 and 10w30's have very little difference at the hot end.

    however, this remains true- anything that has a greater spread (aka, from a straight 30 wt) it requires additives to do that. The additive chains that give the oil to have both cold flow and hot protection do break down over time, as well as oil sheering, so a 10w30 will have a slight advantage over time.

    Loss of a bit of oil pressure can be attributed to all sorts of factors- if your oil pasages are clogged, you will find higher oil pressure! Lower pressure acutally means it is pumping effiicently (that or its not pumping at all!).
     
  13. Drey

    Drey 3/4 ton status

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    Since I bought it...sorry. I bought it with 100,000 miles on it it now had 145,800 something. Since Ive owned it. I have only put in 10w-30 Havoline oil. Changed every 2500 miles. It has received new plugs, new mass air flow sensor, new O2 sensors, new egr valve, new pcv valve. It had been into the shop for some emmissions filter thing to be cleaned out too. Also I replaced the Air filter 2 oil changes ago. So far the motor DOES NOT use any oil and DOES NOT leak any oil. I just noticed a slight drop in oil pressure at about 140,000. It runs consistantly at 195.

    I figure my mileage each time I fill up, I know its never going to be dead on. But I usually put 180 miles on between fillups and its typically about 10.5 gallons


    It came with 225/75/R15s I run 235/75/R15s on it. It has the auto tranny in it, the axles have 3.43 gears. I do some pulling with it, heaviest thing so far has been every time ive moved from college to my rental house to my appt. It got loaded up enough that had a seriously saggy butt. I tow with it once every two months. But have probably have at least 200 lbs of stuff in the cargo area at all times(toolbox, chain etc.)

    I do romp on it from time to time as well.




    I dont claim to be smarter then the person who designed my motor....old habits die hard I spose. Im afraid too that if I start using 5w-30 it will start leaking too. Ive had one oil leaking bastard of a vehicle and I dont really one another...yet
     
  14. rjfguitar

    rjfguitar 3/4 ton status GMOTM Winner

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    Ok, let me clear up a MYTH about synthetic.

    First and most important, it does NOT cost more to run synthetic! Infact annually it usually costs MORE to use conventional. It cracks me up how people figure it must cost billions of dollars to run synthetic because the initial oil costs are double of what petroleum costs.

    It's called extended oil intervals. Petroleum should be changed around 3K or so in an engine that calls for 3K intervals, a high end synthetic can usually go for 15K on a single interval with a correct nanofiber media filter. I will not take the "I'd never run my engine to 15K on any kind of oil" uneducated talk. If that is a person's evaluation on synthetic oil changes, than that person needs to do some research. :wink1:

    Ok, I'm done for the day.:D
     
  15. JpEater

    JpEater 1/2 ton status

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    THat is right on! I maintain a fleet of 40 Ford V8 and Diesel trucks for a construction company. I run amsoil full synthetic in every truck. I do filter changes every 5k miles. At 30K I take a sample, send it in, and have it tested. Even at 30k miles on the oil I have NEVER had an analysis report come back telling me to change the oil. Even In my Power Stroke trucks the oil is clean enough that you can see the writing on the dipstick through the oil. I am not talking about new trucks either, trucks with close to 200K miles and 30k miles on the oil. Why drain oil that is still good?
     
  16. 4by4bygod

    4by4bygod 1/2 ton status

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    How often are you changing that filter? when you change the oil at 15k, or at a shorter interval?

    There really isn't such a thing as a high end synthetic.. even the joe gibbs stuff at 12 bucks a quart is the same PAO / ester blend as mobil one,lucas, RP, amsoil, and all the other synthetics.. it comes down to who's got the biggest marketing budget nowadays.


    Tom
     
  17. rjfguitar

    rjfguitar 3/4 ton status GMOTM Winner

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    I change the filter when I change the oil. You are not supposed to use a cellulose filter with a long lasting synthetic, as the media has less holding capacity and breaks down faster. I use filters with synthetic nanofiber material, it holds more material and lasts longer so no need to do mid interval filter changes.
     
  18. 4by4bygod

    4by4bygod 1/2 ton status

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    gotcha.. do you use oil analysis to see how the additive package is holding up after 15,000 miles?

    Tom
     
  19. chevyryan

    chevyryan Registered Member

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    the only reason why is because its supposed to stay cooler but i dont think 3 mpg. especially with that huge mialge difference between the two
     
  20. goldwing2000

    goldwing2000 Guest

    How does your friend's truck compare to all that. Different gear ratios, smaller tires and lighter loads all change your gas mileage.

    Also, you don't know how well the PO took care of it for those first 100,000 miles (unless you bought it from a family member or something). They might have been using a 10k miles oil change interval and your rings might be shot. You just never know.

    Also, you have a bigger tire than originally equipped, so your speedometer and odometer are now reading about 2% slower than your vehicle is actually travelling. At 60mph, you're actually travelling 61.3mph.
    If you're calculating 18mpg, then you're actually getting slightly better. Not a 3-5mpg difference but every little bit matters.
     

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