How do I know when to replace a fleet vehicle?

Compare the all-in monthly cost of keeping the current vehicle (maintenance, downtime, fuel, and depreciation) to the all-in monthly cost of a replacement (payment/lease, fuel, maintenance, and depreciation). Replace when the expected cost becomes consistently lower.

What costs should I include in a keep vs replace analysis?

Include maintenance and repairs, downtime (lost revenue or rental/coverage cost), fuel, insurance differences, taxes/fees, and depreciation or resale value changes. This tool focuses on the biggest drivers: maintenance trend, downtime, fuel, and financing.

Is downtime really that expensive?

It can be. Even a few days per month of lost utilization can outweigh fuel savings. If you can price a “replacement vehicle per day” or lost job margin, you can model downtime cost credibly.

Vehicle Replacement Timing Calculator (Free) | Moto Watchdog

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Vehicle Replacement Timing Calculator (Free)

Compare keep vs replace using maintenance trends, downtime cost, fuel efficiency changes, and financing. Find the estimated break-even month and export the analysis to CSV.

Keep vs replace comparison

Break-even month

CSV export

Find your break-even timing

Enter your current vehicle costs and your replacement option. The model projects monthly totals and shows when replacement becomes cheaper.

Inputs

Advanced

Current vehicle (Keep)

Current market value ($)

Expected depreciation ($/month)

If unsure, keep conservative.

Maintenance + repairs now ($/month)

Maintenance growth (% per month)

Models rising repairs as vehicles age.

Downtime (days/month)

Downtime cost ($/day)

Lost margin or replacement rental cost.

Miles per month

Fuel price ($/gal)

Current vehicle MPG

Other monthly costs (keep) ($)

Optional (insurance delta, fees, etc.).

Replacement vehicle (Replace)

Purchase price ($)

Down payment ($)

APR (%)

Term (months)

Expected depreciation ($/month)

Maintenance (new) ($/month)

Downtime (new) (days/month)

Replacement MPG

Other monthly costs (replace) ($)

Optional (insurance changes, telematics, etc.).

Analysis horizon (months)

This is a planning model. Swap in your actual historical maintenance and downtime for best results.

Recommendation

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Based on projected monthly totals.

Break-even month

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When replace becomes cheaper (cumulative).

60-mo savings (replace)

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Replace vs keep (cumulative).

Month	Keep (monthly)	Replace (monthly)	Cumulative delta

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Keep vs replace: the fleet decision that compounds

Replacement timing isn’t just about purchase price. The biggest drivers are usually maintenance trend, downtime (lost utilization), and fuel efficiency. This calculator turns those factors into a monthly cost model so you can estimate when replacement becomes the cheaper option.

What to do before you replace

Confirm downtime cost: rental/coverage cost or lost job margin is often the hidden driver.
Use real maintenance history: trend over the last 6–12 months is more credible than guesses.
Separate by vehicle class: vans vs trucks behave differently.
Track cost per mile: fuel + maintenance per mile reveals aging effects quickly.

Replacement Timing FAQ

What if my “new” vehicle is leased?

You can approximate a lease by entering the monthly payment as the “loan payment” (set term to lease length, APR to 0, down payment to due-at-signing).

How do I estimate depreciation?

If you don’t have a model, use a conservative monthly estimate and include salvage values at the end of the horizon to avoid over-counting.

What if maintenance is spiky (one big repair)?

Use the risk buffer and a realistic growth rate. Or model a one-time repair as “other cost” in month 1 (custom version if you want it).

Disclaimer: Planning estimates only. Validate assumptions with your fleet’s maintenance history, actual downtime costs, and financing terms.