Turbocharged Direct Injection (TDI) Volkswagens are powered by a turbocharged diesel engine. TDIs are clean burning, powerful, reliable and fun to drive. Diesel engines are very efficient and operate under much different conditions than a gas engine. Consequently, when evaluating a pre-owned TDI you need to ask a few more questions.

Maintenance History

• What type of oil was used? TDIs need oil specifically designed for their diesel engines as documented in the owner’s manual. Synthetic oils approved by VW for their diesel engines are designed to properly lubricate over long maintenance intervals and to hold diesel soot. Diesel engines are lower RPM, lower heat and sturdier than a gas engine, with proper oil and maintenance they can run several hundred thousand miles.
• When was the timing belt replaced? TDIs use timing belts instead of chains to minimize noise. Unfortunately, the replacement of a timing belt and related parts is very expensive. A timing belt service usually includes replacement of the timing belt, timing belt tensioner, idler roller, water pump and related fasteners. A competent mechanic can inspect the belt for signs of wear. If the timing belt breaks there is a high risk of catastrophic engine failure. Plan on the cost of immediate catch up maintenance if the prior owner didn’t complete this servicing.
• When was the fuel filter / water separator replaced? TDIs need clean diesel that is filtered with any water removed. The filter / separator unit needs to be replaced periodically and is larger than a typical gas fuel filter.

Used TDI Buyer’s Checklist

• Car Fax on vehicle identification number (VIN)

1. If there were any accidents, ask for receipts to assess damage
2. Verify that title is not salvage or rebuilt

• Ask dealer to run warranty and recall history on VIN
• Verify that owner has the following

1. Owner’s manual
2. Keys (2 master, valet)
3. Wheel lock and radio code (if applicable)

• Verify the following work

1. All keys and keyless remotes
2. All power windows and locks
3. Radio, Cruise control, etc.

• Verify that

1. All four tires match and have even wear
2. Coolant reservoir has proper color and there is no coolant migration by unplugging the coolant reservoir and feeling if there is any liquid in it
3. Brake fluid is the proper color
4. Oil and transmission fluids are at the right level
5. Brakes have remaining pad wear
6. Computer has no stored error codes by visiting auto part store for free scan
7. Exhaust system is in good repair
8. Ask seller if they made any modifications to the car (these could have voided the warranty)

Maintenance History

• Receipts make a purchase less risky and help avoid the cost of catch-up maintenance.
• Check if their repair shop was reputable or for a do-it-yourselfer ask detailed questions. Perhaps, they have a left over oil quart that you can verify is oil approved by VW?
• Verify maintenance history against recommended maintenance schedule within the owner’s guide
• Check oil pan for damage since many models have lightweight aluminum oil pans. (I knocked my aluminum oil pan out by hitting a deep pot hole in Michigan. To avoid repeating this repair I replaced the plastic engine underbelly cover with a solid steel skid plate.)

Test drive

• Drive a similar car first that is known to drive well
• Drive at varying speeds (town, highway, interstate)
• Verify that engine and air bag lights illuminate at startup and then go out