New gauge: How much is that in gas?

But the assumption is that everyone reading the advice can afford multiple lattes per week, which is why it irks me.

Suppose it were called it the "free gasoline factor"?

Now that I have your attention, let me share a Frugal Cool reader's recent epiphany: He now views all purchases through the filter of "What's that in gas dollars?"

Where you live determines what you pay for fuel, of course. The national average price is about $3.75 a gallon. The reader, who comments as "Jestjack," assumes a cost of $4 per gallon. Thus his recent purchase of $2 cargo shorts from a thrift store equaled half a gallon of gas.

"I will probably wear these about 75 times, maybe more, in the next couple of years working on rentals," he says.

• Bing: How many lattes do we drink?

Around the same time, a doughnut shop offered coupons for free iced coffee. Without a coupon he'd have paid $2.

Actually, he wouldn't have. Viewed through the fuel-cost filter, $2 for a cold drink just doesn't sound smart, Jestjack says.

Rethink the way you spend

I'm with him. It's not that you should never be allowed to have a treat. It's that you need to take care of business first.

As fuel prices rise, the extra money has to come from somewhere. Unless your salary is rising too, that means rethinking the way you spend. 

Hence the "free gas for a month" factor: a budgetary tweak here and there and you've bought yourself a few tanks of gas. Maybe more than a few.

Your mileage may vary, as it were, since frugality means different things to different people. But certain measures don't require much effort or pain. For example:

• Brown-bagging your lunch.
• Using coupons and/or changing grocery-buying habits.  
• Scoping out free stuff.
• Looking for ways to cut prescription costs.  
• Shopping thrift stores or yard sales. 

Start slowly. Let's say you pack your lunch three times a week for a savings of $30. Assume you spend $10 of that on sandwich makings. You've given yourself a $1,040 annual raise by "finding" money you used to fritter away.

In gas-dollar terms, that’s 274 gallons of free fuel.

And yes, it is free, because this is money you wouldn't otherwise have. It would have been piddled away on small, forgettable things. Like iced coffee.

Readers: What are some of the relatively simple ways you trim expenses?

More from MSN Money:

• Free gift cards -- yes, really!
• 25 freebies for your birthday
• How to get free life insurance
• Yard-sale nirvana: The 'free' box