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Old 08-26-2016, 01:16 AM   #11
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In drafting I would assume then if you can't see then you most likely could not stop in time either.
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Old 08-26-2016, 02:21 AM   #12
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We have found one way to save a few 10ths mpg is to turn off AC when going up hill. Turn on again on more level ground, which is rare in the West.
So it is a good idea to plan your route so as to always be going Down hill!
Especially in the Rocky Mountains...
Of course YMMV!
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Old 08-26-2016, 02:32 AM   #13
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We used to be very careful about mileage. Drive slowly, limit weight of water, etc. As we got the handling of the van better, it got very easy to drive at higher speeds, and when we are booking time to get somewhere or home, we go much faster than we used to, usually averaging 67mph, even in nasty winds. We can afford a little more gas to cover 800 miles instead of 600, if it gets us where we want to be and is not any more effort. Of course, when we are touring nice areas we are going slower, but don't make an effort to wring out every 1/10th of mileage, it is just not worth the hassle.

These days, the only time we do a careful mileage run is to check the baseline mileage to make sure the van is running properly. Not sweating the gas mileage all the time makes the travel way more enjoyable for use.

As odd as it may sound, we get the best mileage in rolling hills. Even better than on flat constant load driving. Surprisingly, the physics actually backs up the actual in this case. There was a thread on this here a number of years ago.
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Old 08-26-2016, 02:37 AM   #14
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Davydd, you're right it is dangerous, will probably do it from farther if that in fact does anything at all. I would say I was 4 car lengths behind at 60mph. I heard somewhere before that race cars at 2 feet get more than 25% more, then it slides from there right up to about 100 ft. I guess it was also the only place to be driving slower than the rest. Never in my driving life had so many bus RVs pass me up !!!

On hills I usually find the sweet spot watching the tachometer & listening to engine sound. It's a bit tricky but I've only driven this 3 times.

AZ, wife & I never turn AC unless it's over 100 outside (always trying to escape San Francisco's foggy summers). I use to drive an old Datsun B210 way back and could never figure out why it overheated so used to turn heater on especially on hill climbs-just to get the temp down.

Mike, my brother in law drives an 18-whlr for a living and he has lots of don't-do-this advice....
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Old 08-29-2016, 08:26 PM   #15
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Just an update on the return trip mileage. As expected the mostly downhill run yielded 15.72 mpg - a little over 6% better. So I'll set my average at 15.2 mpg.
Next goal is 16. The plan is get engine tune-up, change fluids (is synthetic oil really better?), follow weight shedding plan, drive/accelerate slower....and pick a windless day!
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Old 08-29-2016, 08:41 PM   #16
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synthetic oil works great in motors designed for it- with close tolerances.

I have used synthetic 20w50 or 10w-40 since new in my 2001 GMC 4.8 pick up
I have 165k with no problems. Usually mobil 1- $23 at walmart. I change every 3000 miles ( overkill but I live in a high heat, dusty area)

The 20 will be thick enough to move quickly to lube the motor on start up, the 50 will resist break down when it is hot...I may use 10w-40 in the winter if I happen to have an oil change coincide with our 2 weeks of winter.

on most chevs, the oil is easily changed just by laying on the ground and reaching in from the side. no need to jack it up

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Old 08-29-2016, 11:45 PM   #17
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Quote:
Originally Posted by mkguitar View Post
synthetic oil works great in all engines.
I fixed that for you.
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Old 08-30-2016, 04:46 AM   #18
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no-
synthetic doesn;t work well in older motors with loose tolerances- in many cases it will seep out through paper gaskets used between rough castings ( modern motors will use a plasticized surface on the steel gasket to seal nice tight joints

on a worn motor with deposits, synthetic may lift this crud and start it moving through the motor where it can crud up fine passages in the lifters or bearing journals.

as much as I'd like to, I can;t use synthetic in my old 50's, 60's and 70's motors for those reasons.
even older motors rebuilt and machined just don;t have the quality of metals used to resist seeping

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Old 08-30-2016, 12:29 PM   #19
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Synthetic oil is no longer alcohol based. The seepage you are talking about is a decades old issue that is now a myth about synthetic oils, it just doesn't happen anymore. I use Mobil 1 in all of my vehicles including an original, un-rebuilt 1972 360 V8 in my 1982 Dodge shortbox.

The only thing it may/will do is release scale and deposits which can be dealt with by a secondary oil change.
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Old 08-30-2016, 02:45 PM   #20
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I think the synthetic oil arguments will go on forever

I am neither a hater or a great lover of synthetics, so no huge bias, I hope.

I use both, and have success with both. 1992 Escort ran for 18.5 years, 210K miles, of ugly Minnesota commuting. I used Castrol dino oil in it, and when it went to the junk yard it would still go 10K miles without adding oil and never leaked. We went to synthetic in our small engine lawn tractor engine and hydro transmission and they run noticeably cooler.

I also have had issues with synthetic. Several older flat hydraulic lifter engines I have been around would have tappet noise on synthetic. I have seen the leaking issue, and it is not just in engines. I changed my 96 Buick Roadmaster 4L60E to the Dexron VI fluid and got a leak in a cooling line within weeks. Pan gaskets on both trans and engines seem to have issues if they are not the new reusable, inserted spacer, silicone type like we have on the 07 Chevy 6.0 engine. I quit using the regular gaskets on the trans pans a long time ago and use Right Stuff with no gasket, as it is the only way I can get rid of the leaks.

Synthetics have also morphed due to some rule changes in what can be called full synthetic, it appears. Nearly all the major brands that are called full synthetic are now group III oils, or mixes of III and IV, I have been told. Those would not have been able to be labeled full synthetic a few years ago. Again second hand information, but Amsoil and Royal Purple are both said to still be 100% group IV oils. Redline is said to be nearly all group V oil which is a different chemical group that is very slippery and tolerates substantially higher heat.

I did read some information a while ago, that was written by a chemist IIRC. I found it very interesting. His claim was that group II and III oils were pretty much neutral in affecting seal hardening and leaking (this is for rubber seals, not the composition types). Group IV oils were said to soften the rubber seals some, which could help some rotating seals a bit, or make them leak. Stationary seals could start to leak. Group V oils were said to slightly harden rubber seals, which could make the wear faster and leak if rotating, and have less affect on stationary ones. He also claimed that a mix of the IV and V would be the best, but I forget the ratio, saying it would get back to neutral on the sealing, but give a lot of the extra temp and lubrication of the group V to the stability of group IV. He even thought the Redline was putting some group IV into their oils lately, but had no data to prove it.

What we use;

07 Roadtrek (6.0, 4L80E) : Mobil1 5-30 in the engine, Dexron VI in the trans. Amsoil Dexron IV in the power steering hydoboost system (definite improvement), either Redline or Amsoil extreme duty rear differential oil.

09 Honda CRV: All Honda fluids except the engine oil which is Mobil1 5-30. Hondas seem to be very picky on their fluids, and I have seen just too many messed up with non Honda products in the trans and power steering.

96 Buick Roadmaster: (5.7 LT1, 4L60E) (130K miles) Castrol 5-30 oil, Dexron VI in trans, Redline or Amsoil rear gear oil, Redline power steering fluid.

John Deere lawn tractor (17hp air cooled Kawasaki): Redline 10-40 motorcycle oil, Redline 20-50 motorcycle oil in the hydo trans.

Of course, everyone has their own opinions on this topic, and always will!
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