Towing within the range limits as specified in the owners manual should not void your warranty. That dealer is feeding you a line. $500 for an ATF & filter change is insane. Considering you are at 47K mi & you heated up the ATF, you should changeout your ATF again. I do yearly partial fluid swaps on mine- 2-3 drain & fill cycles thru the pan. You have to pump ATF up thru the fill/level check plug hole. Whadda PITA, but easy DIY'er. If your tranny is acting OK, and no more temp light, change the ATF & add an aux ATF cooler to prevent this problem in the future. G/luck
Joel

Thanks for the reply...
I agree with you, I'm going to have some diolouge with both the Isuzu DM and the Service mgr.

Been looking into the fluid change, no problem except the check trans and check engine lights will still be on and the dealer won't hook up and turn them off unless they do the service. I told them that was extortion, they didnt seem to care what i called it, they think they got me!

Damn, I tow 5000+lbs on a regular basis w/o any issues even in the mts upstate NY. And I abuse the crap out of my engine and tranny, so far 61K miles trouble free.

-mike

5-50 is low?

The oil pump is going to be working really hard with a 50 weight oil. 5-50 oil is 'heavy' in my book. The first digit is a guide for the first seconds after start-up (cold start) only. Just because the index starts with a zero, or even five, doesn't make the oil 'light'. At operating temp., under load, and with you sticking the boot in, the oil pump will be struggling to get 50 weight oil out to that distant cylinder in time to make any difference....perhaps.

Mr. Big horn,

5-50w oil is thinner than some of the other varieties like 10-40w or 20-50w...
the oil I use, 0-40w is REAL thin....it pours like water, even in cold Washington weather conditions; on the other hand some "dino-oils" in the 20-50w, pour like molassis at the same temp.

Do you even have Mobile 1 in Japan?

Synthetics have been proven to be more stable at lower (and higher) temp.....therefore allowing the oil to be a wider viscosity and still offer better protection than conventional oils do at both ends of the temp/preasure spectrum......

At low temp, 0-40w flows better than almost any other wide viscosity oil.... and still has the high heat / preasure threashold of a 40w oil. <img src="/forums/images/graemlins/shame.gif" alt="" />

Allan

We're not on the same wavelength here.

You're simply stating the advantages of synthetics...It goes without saying that synthetics are superior lubricants...based on robustness to heat, film strength, purity, stability, "flowability"... etc.

What I'm pointing out is that 50 weight oil is not light. It is heavy.

Motor oil thins as it heats and thickens as it cools, right?

Accordingly, an oil is rated for one viscosity when cold, and another when hot, right?

The measurements are taken at specific temperatures: Precisely, at 0? F (the first number) and at 212? F (the second number), right? (BTW, the W means the oil meets specifications for viscosity at 0 F and is therefore suitable for W(inter) use. It is written after the first number, not the second.)

So, as an example, 0W-40 oil has less viscosity when COLD than does 10W-40. 10W-40 oil has less viscosity when COLD and HOT than does 20W-50. Right?

At the low-temperature end, the first number ( the ô10Wö in 10W-40 ), oil has to be resistant to thickening so that it flows more easily to all the moving parts in your engine. This is particularly important at cold start. Right?

Once the engine is running, the oil heats up. Right? Now, the second number in the viscosity rating--the "40" in 10W-40, for example--tells you that the oil will stay thicker at high temperatures than one with a lower second number--the "30" in 10W-30, for example. Right?

The more resistant it is to thinning, the higher the second number (10W-40 versus 10W-30, for example) and that's good. Right?

Well, within reason. Thicker oil generally seals better and maintains a better film of lubrication between moving parts.

To lubricate the engine the oil must be delivered to the engine by the oil pump, right?. But, if the oil pump encounters too much resistance to flow the pump opens a relief valve and vents the oil back to the inlet... so 50 weight oil will show a slightly higher pressure on the gauge but is it looking after the engine better?

Factory spec. 10W-30 oil will be able to flow more easily throughout the engine at a lower pressure but greater volume. One of the oil's jobs is as a coolant, so large flow rates are favorable, right? In different climates, and in different Japanese engines, it is not uncommon to hear of heavy oils bulging oil filters as the oil pump can't dump enough oil through it's relief valve fast enough.

It goes back to what I said previously. The engine is hot. It's under load. You give it the boot. Load on the engine increases as the RPM climbs. The engine is spinning fast now. It needs lubrication as measured by volume now. In this instant, of greatest need, can the oil pump get thicker 50 weight oil out through all those low tolerance nooks and crannies in the engine? Number 1 cylinder, farthest from the pump...is it being starved of lubricant when it needs it most?

What was the problem cylinder in the Isuzu gasoline engines...?



What's really important is that you use the oil viscosity your car's owner's manual recommends.

--Bighorn--