There are two systems you need to have working perfectly for a diesel to start in extreme cold.

1. A starter and battery in EXCELLENT condition. If the starter is old and tired or the battery is not up to snuff or even if the battery cables are in poor shape the engine will not turn over fast enough to start.

2. Fully-functional glow plugs. The only way to make absolutely sure the plugs work correctly is to pull them and bench test. Older or half dead plugs will test fine electronically but they don't glow red-hot.

Synthetic oil certainly helps cranking speed, block heaters make it easier to start the engine and fuel additives keep the fuel flowing but they are just a crutch if you don't have #'s 1&2 sorted out. RT

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