Cold Weather & MPG/Block Heater
 

It's amazing how much cold weather with snow and ice can affect your MPGs. Here in Colorado (Denver suburb area) we’ve had several big snow storms so far and lots of cold weather. We also had a very mild summer (definitely not global warming this year). Anyway even with a block heater my mileage drops an average of 5 mpgs on snow and icey days … doesn’t help that you carry extra weight with the ice and snow stuck to the wheel wells and under the car.

Also learned using the car interior heater will affect whether the engine shuts off or not at a light. As soon as you hit the off switch on the steering wheel, within a second the motor will quit. I tested this by turning the heater back on and sure enough the motor started instantly. The temp on the SG at the time was around 130 degrees. So if you want to improve MPGs slightly (very slightly) and stopped a long light, shut the heater off!

Speaking of the block heater, not sure I can tell it made a difference. I have it come on 4 hours prior to driving and depending on whether I park in the garage or not, the temp on the scan gauge will be around 128 in the garage and 109 out of the garage. This is with the temps over night in the mid 20 degree range. Perhaps has made some difference, but the easier drive is to work and it is slightly downhill so don’t need a lot of power and the MPGs are normally 5 to 8 better than the return trip. BTW, I have a gauge that will record how much electricity a device is using. I plugged my block heater into this unit and found that running for 4 hours, it uses .18 cents worth of electricity at 11.9 (considers all taxes) cents per kwh. This was the average over about 3 days.

Re: Cold Weather & MPG/Block Heater
 

I put a block heater in the wife's RXh and have it on a timer set to give it about 1-1/2 or 2 hours of warming before she leaves in the morning. With the scan-gauge I see it trims about 5 minutes off the warm-up time, so I use it year-round.

Depending on how much time you spend at traffic lights, the gas used/saved can be meaningful. I put the scan-gauge in my conventional Explorer and watch my 'trip mpg' number go up while I'm moving but drop steadily while waiting at lights.

Benton 29oct09

Re: Cold Weather & MPG/Block Heater
 

Hello to all

Engine heater types, pros & cons (in no particular order)
1) Dipstick heater: replaces your regular engine oil dipstick; the long, thin heating element warms your engine oil
ease of installation: easy
pros: generic; easiest to install; also easiest to transfer to another car should the need arise
cons: smaller diameter element means lower heating capacity; probably the least effective of all types for heating inline heater (non-circulating)
2) Inline heater (non-circulating): splices into the (usually lower) coolant hose
ease of installation: easy-moderate
pros: generic; can probably transfer to your next car.
cons:: coolant in the hose gets hot, but the heat may not transfer well to the engine, particularly if there's a closed thermostat between the heater and the rest of the system
inline heater (circulating)
3) Inline heater (circulating): splices into coolant hose (usually heater core hose), uses built-in pump to circulate coolant over its heating element and through the system
ease of installation: moderate
pros: generic; much more effective than non-circulating inline style; probably best combination of effectiveness vs. difficulty of installation; fastest heater/defroster output
cons: larger size; more to go wrong (built in pump, thermostat)

Thanks for sharing
Have a nice day

Re: Cold Weather & MPG/Block Heater
 

Thanks Tom for you detailed input on your block heater.
I feel better knowing it don't cost much at all to use it for hours. My theory is using the block heater helps the engine to heat up much quicker.

Like you said, your engine was up to 109 degrees while sitting outside on a 25 degree morning. That would sure beat your engine being at 25 degrees when your started it for the day. The spark plugs are a lot more efficient when they are above 160 degrees. The block heater makes that possible a lot quicker.

I do know the fuel injectors run rich till the engine heats up to a certain temperature. If it's cold enough like 12 to 18 degrees the injectors may stay somewhat rich. You may also notice when it's that cold, your engine heat SG reading will be well under normal.

I remember my 4-cyl 2003 Corolla got 42 highway during the summer at 60 mph. We went on a 600 miles trip to Dallas and the temperature dropped to 12/14 degrees for the whole trip. No matter what speed I drove, the car dropped down to 21 mpg according to the scan gauge.

My TCH has already dropped 4.3 mpg with this cold weather. Tonight I had trouble getting into the ev mode. I forgot about the heater fan being on low. I usually turn up the heat to 89 and fan and to heat up the cabin. I turn the heater fan off across this same couple miles where I know the TCH usually goes into the ev mode.

Re: Cold Weather & MPG/Block Heater
 

4) The OEM type (for Toyota Highlander or Lexus RX at least) involves pulling some shrouds from around the exhaust manifold (?), and removing a plug from the block and replacing it with a heater plug.

The part isn't terribly expensive ($30-40?) but there is some labor involved whether you do it yourself or have a dealer install it. There is an installation write up circulating on one of the 'green' sites.

If I'm recalling right, it burns 550 W, so 1 kWh in just under two hours. I run ours for around two hours, so about 7-8 cents a day here.

There was some concern expressed by someone in another thread that shorting the engine run-time this way might keep the catastrophic converter from getting properly warmed and so might shorten its life.

Benton 31oct09