Brits in an RV - Denver to San Francisco

That's a pretty big loop you are planning, so don't try to fit more in the "shoebox" than will fit. :)
from denver to moab on 70 and 191 is good, but there is a scenic byway you can get at exit 212 off I 70 that will take you along the CO river into Moab.
From Moab down to 163 down to 160 and west to 89 then into Grand Canyon via 64..all passable roads, two lane. this is not a crowded area of the US, so there will be miles and miles of vacant land between a few small towns, but all the towns will have fuel. Kayenta, AZ, in the middle of american indian country, has a good sized grocery store if you need to get anything before going on to Grand Canyon.
From GC, on west to Las Vegas. 93 from Kingman up to Vegas is good and will cross the CO river on a very high bridge, but they require the trucks and rvs to use the inside lane. plenty of room.
Do skip Death Valley and Mono Lake at this time of year. It's just not worth the discomfort, and the grades going down and climbing out of DV are really pretty tough. Barstow to Bakersfield and north is good, and if your time is good, take 198 west and north out of Visalia and drive up through Sequoia Nat'l Park before going on to Yosemite. Sequoia has the big trees and it's a very scenic drive, etc.
Crossing NV and UT on I 80 is pretty boring...all high desert country but it follows, roughly, the way of the first intercontinental railway. And in UT you will pass by the Salt Flats where they test high speed cars and motorcycles... like in the movie "The World's Fastest Indian" with Anthony Hopkins. I think there is a viewing station along the highway you can stop for a break and maybe see something of the testing area.
Have fun.

I agree with ksg5000: visit Capitol Reef NP, Bryce & Zion. Three great NP's in Utah and all worth visiting. Make sure you go to the historic little store at Capitol Reef and get the homemade pies and even scones made by a Scotsman! You may also consider stopping in Palm Springs/Indio area for a few days. Paso Robles and wine country rv park is worth a visit, particularly far out wineries. Then go up the coast to Big Sur and Monterey on highway 1. Scenic drive and narrow in some places but easier going north. Do the 17 mile loop around Monterey & Pebble Beach. On the coast just west of Paso Robles visit the Hearst Mansion, San Simeon. If you can fit it in and plan a route, Yosemite and Sequoia NP worth a visit. Monument Valley is good for a quick stop and a few pictures, but not much more. Roads are not that great.

Here is a rough idea of a route I would take: Denver I-70 west to Moab exit. Back to I-70 then on to Capitol Reef, Bryce and Zion. From Zion get on I-15 south through Las Vegas, to Bakersfield and Paso Robles. Then over to Highway 1 and up the coast towards San Francisco. The Grand Canyon is spectacular, but it takes you a few miles out of your way. If you have the time, go there from Bryce then back to Zion.

On the way from Grand Canyon to Vegas consider hitting Zion/Bryce Nat't Parks - easy Google.

Ok that's Mono Lake off the list! :)I remember seeing a pic of it many years ago and the image stuck with me ...
Many thanks for the tip on driving downhill with an automatic box ,, hadn't occurred to me that I may cook the brakes.
On another post I have seen someone recommend North Rim road from Jacob's Lake to North Rim Grand Canyon Lodge so I will try and fit that in too. In total we have 3 weeks to complete the trip so any slight diversions are definitely doable.
Time to amend the original post and cross Mono Lake off the itinerary!:S

I would also cross Mono lake off the list.

Even Bass Lake is better than Mono Lake. And it is close to Yosemite. Corsegold has some full hookup campgrounds, while Yosemite can be difficut to get reservations for a overnight stay within the NP, yet Sequoia NP had some first come first served no reservation campgrounds the last time I was there. To get a good spot there, arrive around noon, and pick a campsite. It normally is not full except friday afternoon to Sunday around noon.

Fred.

Hi,

While you are used to a manual transmission, all of the motorhomes are automatics here in the states. You normally would downshift the car while going down a steep mountain grade, yet will tend to forget about it in the motorhome. Make sure that you know how to and lock out overdrive when going down the hills, instead of riding the brakes.

When crossing Death Valley, I suggest doing that at night, when the temperatures are only around 100F. Daytime high today is going to be 120+. Yes you can run the generator and rooftop A/C, this is what I do when in the mountains, to give the dash A/C a break while climbing the hills. Yet you might have a generator hour time charge, if you exceed say 10 hours on your rental time.

Your plan looks great. But you might want to ask about going from Las Vegas to Mono Lake. And I question Mono Lake, it is a big 1/2 dry lake - why there? Mammoth Mountain is much prettier. June lake - very scenic. But mono lake?

Personally, knowing how hot Death Valley is, I would go from Las Vegas to Barsto, then west to Bakersfield, then north to Fresno. Fill up with gas there, because in the mountains they need to truck in fuel, and it can get expensive. Take highway 41 to the Yosemite entrance. Turn to the right, go 2 miles to the Grizzley Giant, a tree that is 27' across at the base. Then go to the valley. Perhaps catch Glacier Point.

I would rather spend a day in Sequoia NP than Mono Lake.

Fred.