One of my favorite features in Motley Fool Champion Funds is Shannon Zimmerman's monthly update on exchange-traded funds (ETFs) and index funds. Though I'm a stock investor at heart, I believe almost everyone should have index funds at the core of their portfolios.

But there are some index trackers out there who will cheat you out of your hard-earned dollars if you're not careful.

Fees are heading downward
A small revolution is under way in the industry, and it's been very good news for you and me. Vanguard, Fidelity, and some of the other big index-fund providers -- perhaps under pressure from low-cost ETFs -- have been lowering the management fees for their products.

Take Fidelity Spartan 500 (FSMKX), for instance. If you have at least $10,000 to invest, you'll now be charged only a minuscule 0.1% expense fee. If that $10,000 is too high of a hurdle, you can start with as little as $500 if you use the "automatic account builder" option, which makes automatic deposits for you on a regular schedule. Another option is the stalwart Vanguard 500 Index (VFINX), which charges only 0.18% and carries a minimum initial investment of just $3,000.

So those two provide a baseline comparison for any S&P 500 trackers. What about other index offerings? Let's take a look at two mid-cap index funds that seek to duplicate the S&P MidCap 400 index. Both have Peabody Energy and Expeditors International as their top two holdings. And glancing down the list, you'll see many other similar companies:

Dreyfus MidCap Index (PESPX)
Major Holdings*

First American Mid Cap Index (FDXAX)
Major Holdings*

Cognizant Technology (NASDAQ:CTSH)

Cognizant Technology

Noble Energy

CH Robinson Worldwide

Smith International (NYSE:SII)

Smith International

Precision Castparts

Noble Energy

CH Robinson Worldwide

Precision Castparts

Questar (NYSE:STR)

Ensco International

Ensco International (NYSE:ESV)

Microchip Technology

Microchip Technology (NASDAQ:MCHP)


Expense ratio: 0.50%

Expense ratio: 0.75%

*As of July 31, 2006, for Dreyfus. As of June 30, 2006, for First American.

Same objectives, yet First American's expense ratio is a full 25 basis points higher, and you may have to pay up to a 5.5% front load! What's more, you'll pay a stratospheric 1.5% for its Class B and Class C shares for this same fund. Dreyfus' 0.5% is much more reasonable, yet even that is high compared with Vanguard Mid Capitalization Index (VIMSX), which charges 0.22%. (It tracks a different mid-cap index, but that's still no excuse for Dreyfus and First American.)

If you're an aficionado of small caps, Vanguard Small Cap Index (NAESX) gives us a good idea of a low expense ratio in that space, charging just 0.23%.

Don't get cheated
When it comes to index trackers, you can expect that, on average, your fund will lose to the index by the amount of its expense fees. And while the gap between, say, 0.75% and 0.18% may seem small, it's actually a huge difference that will cost you big money -- potentially hundreds of thousands -- over the years. "With that in mind," Shannon says, "there's simply no reason to pay any more than you absolutely have to for a fund that merely tracks a benchmark."

Check out your index fund's expense ratio to see how it stacks up with competing products. Keep in mind that Vanguard's and Fidelity's low-cost offerings range from 0.1% to 0.23%. If yours is significantly higher, you should definitely consider moving your money into a lower-cost fund that tracks the same index.

More fund fun
The monthly "ETFs & Index Funds" feature in Champion Funds is an interesting read that can profit any index investor. It certainly caused me to scrutinize my index fund's fees.

Shannon is offering a free trial to his newsletter, which will grant you access to every pick he's ever made and every index-fund column. His recommendations are beating the market and equivalent benchmarks 20% to 11%. Try it for free for 30 days, and if you don't like it, it won't cost you a penny.

This article was originally published on Jan. 6, 2006, as "When to Dump Your Index Fund." It has been updated.

Rex Moore indexes in his 401(k). He does not own shares of any company mentioned. This information is brought to you by the Fool's disclosure policy .