Mileage Improvments with synthetic oils

[Metrodps]

Ok so the DP Suburban has 350 tbi with a 4 speed (granny low) manual trans and [FONT=&quot]3:73 axles. When I fist got it I did not have any thing hanging on the roof and going to Moab a few times it got 13.8 mpg.

I put the synthetic motor oil in engine and put Royal Purple Maxgear75-90 in the axles. With the roof rack, lights and 33" tires I have been getting 15.3 mpg on highway. So the next step is to get some Royal Purple Max ATF for the transfer case (3 quarts) and see what it does.

[/FONT][FONT=&quot]O'Reilly Auto has the MaxGear on sale for $14 a quart and I am wondering about the transmission. I have heard since it is a syncromesh synthetic won't do much to help.

I am hoping to be able to get the mileage up 16 would love to break the 17 but we will see.

And one more thing there is so much BS on what type of fluid to use the transfer case that a person could screw there truck up. One say if it is manual tran use gear oil and another says use Dex trans fluid. I spent all week end making sure that I get the right fluid for it.

I am starting to look at different air filters to see which gets better mileage. The K&N helped the Blazer but when I pulled it for a cheap O'Reilly one the mpg went up. So next summer I am thinking try the Fram. What have you all done to squeeze a few MPG?
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[Stomis]

Fram make garbage product FYI.


The sm465 is suppose to be gear oil. Ive never heard of it being ATF in my life. Syncromesh is for the NV series of transmissions NV1500,3500,4500, and probably the 5600 too.

Fluid changes are not bull****. Its been dyno proven from conventional oil to synthetic you can pick up 10+ hp.

 

[454Sub]

Tcases also dont use gear lube anymore. But GM can run up to 3 different kinds depending on the case, some use standard ATF, some use synthetic only ATF, and some use GM's Autotrack transfercase fluid, its blue, expensive, and like the 4500's lube, a joke.

 

[kennyw]

I ran ATF in my '79 K10 for 250K miles without issue. Same with the 10 spline NP205 behind it. I replaced two motors in that time with zero transmission or tcase issues.

 

[Stomis]

Tcases also dont use gear lube anymore. But GM can run up to 3 different kinds depending on the case, some use standard ATF, some use synthetic only ATF, and some use GM's Autotrack transfercase fluid, its blue, expensive, and like the 4500's lube, a joke.

Synchromesh is not a joke...

You'll cook the synchros in under 20,000 miles.

 

[dyeager535]

Air filter change making an MPG difference will be miniscule at best. AFR never changes when it comes to what the ECM dictates (to put it very simply) so if your MPG changes due to a filter change, it's from the engine having to work less to pull the air/fuel charge into the cylinder. The filter would have to be nearly plugged to cause a real issue, and would probably collapse if it were bad enough to make a real difference on economy.

In essence, if the filter is bad, it would be no difference than running a too-small throttle body/carb, and at cruise, where you make your economy numbers, the CFM requirements are nowhere near enough to tax the flow capabilities of a filter made to flow enough under WOT, at double the RPM's. So even if flowing say, 50% of what the filter did when new, at cruise the engine is still easily getting enough air, where at WOT it would probably show as a restriction.

No real question on transfercases IMO. Run what GM spec'd. 208/241 never spec'd gear oil to my knowledge, only ATF which leaves the 203 and 205 out there for our trucks. 203 was always engine oil IIRC. The 205 went to ATF later on, but being built/designed/made originally for gear oil, using gear oil doesn't seem to cause any issues. Been running gear oil in my "ATF-era" 205 for ~5 years now.

The only "problem" running ATF behind the 465 is if a seal fails, at which point the fluids are contaminated. Knowing the 465 I doubt that would be an issue, but I'd not want gear oil in my chain drive case for an extended period. It very well may work out alright, I bet there are people that have done it, just not something I'd feel the need to experiment with.

 

[blazer74]

I Don't buy it, Heavy truck, flat front, big tires, roof rack. Never tell the difference with different oils.

You would have to drive the same roads, same speed, same direction, same temp/humidity, same wind speed/ direction to have a correct comparison.

Better off with a good coat of wax on the truck.

 

[82355]

Speedometer correction with the over sized tires?

Martin

 

[Metrodps]

I have waxed it twice! But in re the speedo. I use my GPS set up and it gives me mileage the odometer miles is off by 1/10 per mile or 10 miles for every 100 it shows you add 10 miles to it. When odometer reads 55 your doing 60.

The testing was done on the same road several times. I have to to Ohio Thursday for my mother so I will have 1,568 miles of highway to verify. The only thing that is not synthetic id the gear box oil.

 

[blazer74]

I hear you, 10% increase 13.8 to 15.3 just seems to good to be true.

15.3 pretty good anyways.

That's quite a trip, be safe.

 

[campfire]

[FONT=&quot]What have you all done to squeeze a few MPG?
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Switched to a diesel.





Increasing the tire size will correspondingly change the effective gear ratio. A 10% increase in tire size (as indicated by your speed corrections) would decrease your engine speed at a given vehicle speed by the same amount. Your current combination is approximately equivalent to running 3.36 gears (if such were available) with your old tires. Which should give higher mileage and lower power output comparatively. This mileage gain is often canceled out by the higher stance that bigger tires (and lift kit) typically bring, but I've seen it work out both ways. In your case it looks like it may have helped you more than the lift kit hurt.

Looking forward to seeing how the Ohio trip goes! If there's much wind I would expect the trip out to be noticeably better than the trip back, mileage-wise.
Let me know if you need a place to crash for the night in Iowa.

 

[4xcrazy]

I've never really even considered being interested in any MPG gains switching to synthetic oils, I was more impressed with the way the engine looked after several thousand miles when torn apart and see the difference in crud built up between the two types of oil.

The fact synthetic can handle heat better, lasts at least twice as long and doesn't sludge up an engine was enough for me.

I just recently changed the Avalanche back to a full synthetic, I put 20/50 conventional in it to see if it would help cure a noisy lifter tick at start-up, which it did, but I recently found some 15/50 full synthetic. Still all quiet, oil pressures good and no odd noises.

It's just a cleaner, more tolerant oil to use with a double lifespan than conventional, sure it's double priced, but you're still getting the heat tolerance and cleaner oil.