Oil weight question: 0w30 or 5w20?

[MetroMPG]

It's been a while since I could buy 0w20 around here, and my remaining closest choices are:

• 0w30
• 5w20

For optimal FE, which should I get? Keep in mind that this will be the Blackfly's "winter" oil.

I'm thinking: 5w20 because:

• the block heater will be plugged in before most cold starts, so the lower number (0 or 5) is less important than the higher number
• 20 is less viscous than 30 = more energy savings

Have I got that right?

[Lazarus]

For engine longevity I would go with the 30W but that just me. You don't drive enough to worry about wearing out the engine. With the block heater I don't thing you would see much difference in FE between the 2 because you would be skipping most of the warmup stage where the real FE benefits of the thiner oils come in. Here's a site for oil requirements. Just curious what does the manufacture recommend?

[MetroMPG]

5w30 is recommended. But the car was built before 0w30 or 5w20 were widely available. I wonder if they would have spec'd differently...

Then again, in addition to being gas miserly, it was also built to be cheap. The bean counters probably would have had issues with putting in pricier, low viscosity synthetics.

[Lazarus]

I would think it would have more to do with CAFE standards. Are they still making a version of the flea? If so what are they spec'd for?

[MetroMPG]

Not in Canada or the US.

Though a visitor to MetroMPG recently wrote to tell me that he was in Mexico recently and saw what he thought were "new" looking final-generation Metros driving around.
I have read of car companies sell entire assembly lines for out of production vehicles (all tools & dies) to other countries.