Oil for Extreme Winter Temperatures

Dear Click & Clack,

I have a 1977 Tioga motor home mounted on a 1976 Chevy 1-ton chassis. The engine is 400 cubic inches and the RV has 94,000 mile on it.

As a celebration of my 60th birthday I will be taking a 3 month “Skibatical” beginning January 1st. I plan to live in the RV for 3 months this winter as I ski bum through British Columbia, Montana, Wyoming, Utah & Colorado.

I am expecting to encounter the coldest temperatures in British Columbia and Montana. Realistic temperatures will dip to -20 or even colder on some nights and mornings creating a challenge for engine starting.

Most miles will be on snow covered 2 lane highways during the coldest temperatures. However, traveling to British Columbia from Boise in January and returning from Colorado to Boise in late March will be freeway driving at 65 +/-.

I have always run 10W30 oil. I plan to switch to 5W30 for this trip. Is this the best weight of oil to use or should I run straight 5W or even switch to synthetic for this once in a life time adventure?

Should I change the fan belts, radiator hoses and heater hoses prior to leaving on the trip? They were last changed in 1995 at 72,000 mile.

In case you were wondering, I have all new tires and shocks, a complete brake job including master cylinder in 2008, radiator and transmission flush and differential oil change in 2007 and self performed tune-up in 2007. The thing runs great.

By the way, I do occasionally experience vapor lock in the fuel system, but due to the winter driving I am not anticipating any problems with that ailment. Do you think this is wishful thinking?

I look forward to your expert opinions and advice.


Bruce “The Ski Bum” Larabee,

Boise, Idaho

I wouldn’t go with straight 5w.

I’d go with 5w-30 Full synthetic.


What’s your truck/automotive background?

Drove cars and trucks in North Dakota for years, which for cold is as bad, and often worse, than anyplace you’re going. Also, long-time driver of your destinations. Forget the oil. 10W30 will do just fine. Also, you don’t need to waste any money on preventative replacement of hoses, belts etc. Given that big old 400cc, and if you don’t have one, throw on a tank heater and take along a 50’ extension cord. At least for very cold nights, stay where you can plug in. It will save you some gas, make the mornings comfortable, negate the oil issue and, most importantly, prevent big-time starting drain on the battery. Pay a mechanic $75.00 or so just to go over the whole unit. He will check your hoses and belts. For sure buy AAA+ and take a cell phone. If winter out West is new to you, don’t worry about the passes. Just take your time. Worry some about icey patches (usually overpasses). Snow covered will be the exception - not the norm, even on two-lane. Worry a lot about high winds. Make high winds #1 when you check the weather. …and after that HAVE A BALL.

Appreciate your advise!

You need to know, C&C never, ever respond here. You’re stuck with the participants in this forum. So take our advice accordingly, but from participating here for a while, I’d trust this group easily as much as C&C, we’re just not as funny!

Regarding your question, I agree with Mike. Also, I bet you’ll see temps below -20 if you’re at altitude in BC, etc. Do you have a generator? Is it also set up for cold temps? And is your RV well-insulated as far as water tanks, etc?

You want to run a 5W-30 regular oil or a 0W-30 synthetic oil.

The 10W-30 oil will become too thick when temperatures drop below freezing. The “W” in the oils rating reflects it’s “WINTER” weight. So a 5W-30 oil will flow to criticle engine components much quicker than a 10W-30 oil will when the temperatures drop below freezing.


The 5W30 synthetic recommendation is right on! That will allow easy starts at any temperature you will encounter. Make sure your coolant is good for -40F; that’s a standard 50/50% water glycol mix. 5W is an obsolete spec. for cars and trucks.

Agree with other’s good advice. Since you have not changed the belts for quite some time, I would do that too. A cold overnight stay in ski country can make an old belt snap when starting the engine.

Have a great holiday.

Bruce, you are getting advice from automotive engineers, lubrication engineers, experience auto mechanics, and very knowledgeable owners.

If you plan on living in this thing for 3 months with outside temps being well below freezing. I’d be more concerned about how you plan to stay alive rather than the truck. Condensation from your breath alone will form and freeze to the interior of your RV.

A good furnance will keep the interior nice and cozy. Owner should have it checked out.

5W-30 and change the 15 year old belts and hoses…Install a new set of “winter” wiper blades and a plug-in block heater. Make sure the heating and defroster systems are working properly. Bring the title with you just in case…

If your engine burns a little oil you can continue to run with the 10W-30 dino oil. If you anticipate a very cold morning, then add a quart of straight 10 or even thinner oil at least a few miles before you park but don’t, of course, overfill. You can do the opposite if you run into very hot weather. I have done this and also have left room in the crankcase for a quart of thin or thick oil to be added when I know what the morning temp will be. You can safely run your engine a little under the add mark on the dipstick but I would check it when buying gasoline. My qualifications are that I have lived in the upper midwest US all of my life and owned a motorhome for approx 12 years.

Great, thanks for the background info!

Thanks for the comments

Thanks for the advise. I never knew the meaning of the W. Thanks for that bit of information!

Will be using a portable electric heater when the generator is running and a propane catalytic heater through the night. I have a working carbon monoxide detector in the RV.

Have been using the Catalytic heater for over 10 years with very good results. However, those have been 1 & 2 night stays and all above O degree temps.

A lot of good advise here. I’d add check your battery. A strong battery will crank an engine with cold oil, a lot better than a weak one.
If you can’t find a block heater, there are magnetic heaters available that require no installation, just let it stick to the bottom of the oil pan.
You can save some significant electricity with a timer, set to turn the heater on a couple of hours before you intend to fire up.

For your vapor lock, be sure that the fuel line or in-line filter isn’t touching any part of the engine.

I have read all the material on synthetic oil over the years. Now that is all I use. However, when I drove cars of the era you have, each and everyone started leaking, usually the oil sender, as soon as I put in synthetic. I would recommend using the same type of oil you have always used, except I agree 5W-30 weight for the cold weather.

Look at the oil once in a while on your trip, and if starts looking cruddy, change it no matter how many miles it has.

I could not seem to find what you said about the battery, but if that battery is not almost new, I would recommend putting in a new one, I am partial to the yellow ones from Sam’s Club (does Wal-mart sell the yellow ones?). You aren’t talking a fortune, but the battery is the key to your success in the cold, assuming the charge system works okay.

I, too, think the potable liquids in the cabin are the worry. For a not totally outrageous amount of money, you can get a sleeping bag rated to -30 degrees, but you don’t want your pipes frozen.

By the way, any time I drive in the snow belt, I take my -30 sleeping bags with me, just in case we get stuck out on the highway by a storm.