New to us, GMC Yukon Denali..... Hybrid
 

So, my wife has always been drawn to big SUV's, particularly the black and chrome variety :rolleyes:. We were looking at the last generation Yukon Denali and Cadillac Escalade. Those 6.2 V8's are fun to drive but thirsty AF.

We found a hybrid Denali 4wd and pulled the trigger. On the 50 mile trip home we got a solid 22mpg indicated with 33psig in the tires and 30°f outside.

We've got a 1000 mile round trip over Thanksgiving so that should give us a real good indicator of highway mpg.

It's very odd honestly, this monster truck behaves a lot like my volt as far as how the hybrid system operates.

I won't be driving it much but I'll try to at least get the two highway tanks recorded here. Anything you want to know about it, just drop a line.

Run it on cruise control constantly. And just below the flow of traffic. 2-3/mph below posted on less; maybe 67-68/mph.

Ideally, never change lanes. Avoid packs of vehicles by cancelling cruise until they’re away.

Your drive time won’t change enough to run faster. That’s eaten up by traffic volume problems.

Tires to recommended pressure.

Plan all stops in advance. Two hours or 100-miles apart, roughly. Have that done the night before.

Someone who sits in the Interstate left lane (illegal, only for passing, not overtaking) is doing a bad job of of driving. Risk too high. And costs go up.

When convenient, bring all factory service to date. Time, not just miles.

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Well we found a treasure on our first fill up. My wife went to reset the trip computer and found that not only the previous owner but the original owner also NEVER reset the trip or the gallons used. Lifetime mpg of 19.56

I filled the tires to 40# the night before, with warmer daytime weather they were sitting about 44# during the drive. I think I'll keep the tires at 40-42 as a goal, above that the ride starts to suffer.

Also, on the drive down we seemed to settle in to 20.5 mpg at 75mph. Then we set the cruise at 78mph and also got into some pretty heavy head/cross winds probably around 20-30mph, mpg suffered to around 18.

With two kids in the back and minimal traffic, fuel economy is icing on the cake and not the primary goal.

Neither was safety a goal it appears.

The police-spec Tahoe’s are heavily modified (lowered) to run those speeds.

Pickups and their SUV progeny are SOL if anything goes wrong from 60-mph+

Today’s tires and electronic stability band-aids don’t change physics.

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:thumbup:
I'll take my chances.

In other news: I can confirm that higher speeds definitely reduce your mpg's.....:D:D

I'm really curious what slower speeds will provide. Tooling around town tonight we got about 23 to 24 so this hybrid platform is definitely capable of significantly better mpg than the non hybrids. Even touching non-hybrid v6 sedan territory.

23+ mpg City from a 6L V8 hybrid?

That is better than I thought :)

@Slowmover: Correct me if I'm wrong, but I think the Police Spec Tahoe and the Tahoe Hybrid have a similar (re: lower) ride height

I've found these interesting for a while now and wondered how hard it would be to get 30+mpg highway.

I would say that's not gonna happen. I found it can cruise around 40-60 mph at about 28mpg +/- 10%.

It does seem to happily drop out of v4 mode and run all 8 cylinders with relatively little demand.

These were fairly ideal conditions. About 55°f outside, speeds under 45mph, fully warmed up engine and transmission (driven 150 miles just a couple hours earlier).

I meant with some ecomodding!

Kammback? :D

IIRC it's not only about the ride height, the Tahoe PPV has some differences on its frame in order to alter the center of gravity. I just don't remember how it was achieved.

I'm sure the rear could use some touching up!

How much did they do to the belly of the beast? IIRC they have a large air dam. I'm curious how much the underside can be improved.

Notice any weird things about it? Does it come with LRR tires?

No, on the lrr tires. It needs new and I just ordered a set of Cooper Discoverer SRX 285/45/22.

I have not had the chance to crawl underneath but I dont have the large air dam on this. I dont believe the denali got the larger air dam, but the lower grille is blocked from the factory, possibly on the non-hybrid also.

This is my wife's car so absolutely no mods, unless she doesn't know and can't see them.:D:thumbup:

Stealth mods FTW. Some clear plexiglass for a grille block? :thumbup:

Put 60 PSI in those new tires and let us know what happens.

Those 22" wheels and tires(original) weigh about 96 pounds. Huge potential to drop that. Plus your tire guys will hate you less. Cooper discoverers are pretty meaty, so you may have made your wheel assemblies even heavier than OEM.

Make sure to check the spare!

There is no spare. I will experiment with pressure, but I think 42-45 is my limit right now. I will say, at the factory pressure the tires are very squatted and just look flat.

I got a deal on these coopers and they are comparable in weight to the dueler alenza that are stock. The 22's are staying, not a chance we'll get rid of those.

Honestly, I'm not terribly concerned with mileage at this point. And certainly not open to changing the looks, it's my wife's car and I prefer being alive.

Another interesting note: these are toyota NiMH battery cells used in the hybrid pack.

59MPH is the optimal speed on the the highway(it's down hill from there)
41MPH in optimal in the city OR auto stop 0-29MPH



testing I have done over 4,000 miles

Our Yukon also has the lowest gears available, I believe 3.08:1. Typically that would be a good thing but I think it is reducing our ability to stay in 4cyl mode. Above about 64 on flat pavement it likes to keep running as a v8.

Cruse Control?
Hows the Oil pressure?


3.08 is highway gearing. Tall Gear. if it had a shorter gear it would run higher RPM engine speed
i.e 3.23, 3.42, 3.73 or 4.10....


The shorter the gear(higher RPM = more fuel used) the more fuel consumption...

The hybrid has a lot of torque.. :)


you could put taller tires or shorter tires to change the Final ratio as well...

Yes, we use cc a lot.

Oil pressure is great, might benefit from an oil cooler, after a couple hours driving it gets down around 40psig.

No offense intended, I do have an engineering degree and have been wrenching since I was old enough to turn one. I am well aware of gear ratios and the effect on engine load and fuel economy.

My point is, with numerically higher rear gears the engine would be under a lighter load allowing more use of cylinder deactivation.

Yes but the electric motors have a lot of torque.
so it benefits with the 3.08 ratio...

6qt of 5-w30? or 0-w30?.. mine runs at 55-60PSI@1500 rpm on the highway 50PSI idle....


FYI my last fill up came in at 25MPG Combined (247miles)

19-MPG City
31-MPG Highway
25-MPG Combined
(US MPG)
40% city 60% highway

If you want your V4 mode to work better at higher speed I suggest using 91-93 OR E30-E85 (only if you got a FLEX Fuel..)

get it from a name brand like Chevron or Texaco I seem to have the best luck other gas stations seem to be pumping 87 at the 91 price ( I could tell since I was keep dropping to 3rd gear were it did not on 91octane)

in v4 you lose power because of the retarded timing because of engine AFM stuttering...


the AFM stutter with 87 octane fuel sucks I see more v8 mode and 3rd gear with 87 octane then with 91 octane fuel.

(highest here unless you get racing fuel but not worth it since it cost almost 10$ a gallon)

The oil is whatever the mfg specs and the dealer puts in. Oil pressure is similar to what you describe, go for a 2+ hour highway drive and report back. When the oil gets hot the viscosity drops and pressure goes to around 40psig cruising.

Don't forget this is a hybrid. The electric motors are also the generators so the hv battery can feed the 12v system.

At highway speeds the electric motors are just along for the ride and power is coming primarily from the engine. Even if the electric motors are providing motive power, that power is also coming from the engine which would mean again, it has to work harder therefore would benefit from numerically higher rear gears.

Edit: would benefit by staying in V4 more often.

I have no doubt we would get similar mpg to what you are if we lived in a warmer climate, had lighter wheels, had the aero improvements, and had 2wd not 4wd. I do love this vehicle though!

Have you cleaned out the HV battery?

the blowers in these HV are pretty much dust collectors

I cleaned the screen in front of the motor but I didn't remove the case. It didn't look too bad so here's to hoping i don't have any trouble!

I want to service it my self I just have to get the High voltage gloves..and a mutimeter (premium brand name)


if they had dogs inside it could be a issue

the dealer wants 179$ to service it every 7,000 miles which is a bit nuts


10-15k is fine (mild cleaning of the fan)



the bus bars could have corrosion on them which would cause some impedance(premature battery failure) etc.. Poor Performance

says you will need boric acid NiMH (to neutralize anything that leaked out) and catsup to clean the bus bars (cleans Copper up like a shinny new penny ..)

I would think that unless you had water intrusion or some kind of metallic dust getting in there, cleaning battery connections should not be a normal procedure. Even under the hood, most 12v batteries stay clean and corrosion free. Inside the cabin in an enclosed battery case? Forgetaboutit!