To date-stamp a diesel price for a bid, record its source, measurement date, publication date, retrieval date and rounding before it goes in. A diesel price with no date on it is hard to defend. Bids are reviewed weeks or months after they go out, owners audit fuel assumptions, and a number that looked reasonable when you typed it can look careless by the time the contract is signed.
This post uses three national diesel figures from recent trade coverage to show how to do that. Treat them as examples of how to record a number, not as numbers to copy. Pull the current value from the source on the day you price the work.
Why the date matters more than the number
Diesel prices move from week to week, so a figure is only as useful as its timestamp. Undated numbers cause three kinds of trouble. A figure gets carried over from an older estimate unnoticed. A percentage change gets paired with a dollar figure from a different date, so the two no longer describe the same comparison. An article gets cited as if its publication day were the day the price was measured. Trade publications often report figures after the underlying data was collected, so those two dates are rarely the same.
A good date stamp removes all three problems. It records the measurement date, the publisher, and the day you looked at the source. If someone asks you to check the number a month later, you know which value you used and where to find it again.
The stamp also protects you when a bid is reviewed by someone who was not in the room when you priced the work. That reviewer has only the document in front of them, so the stamp has to carry the reasoning.
Figure 1: $6.179 a gallon on the 12th
Transport Topics, citing Energy Information Administration data, reported that the national average diesel price reached $6.179 a gallon on the 12th. You can find the coverage in the Transport Topics fleet cost article, which also sets that reading against a year-earlier figure.
The day alone makes the stamp incomplete. A bare "the 12th" is not a date, and an owner cannot check it. Before you use this figure, open the original article and copy the full date. Write it as a complete line, such as "EIA national average, [month] 12, [year]: $6.179 a gallon," with the month and year filled in from the source.
Name the series as well as the number. Publishers revise figures, and a series name tells a reader which dataset the number came from. "National diesel price" means little on its own, but "national average, as published by EIA" tells a reviewer where to look.
Keep the measurement date and the publication date apart. The measurement date is the day the price applies to. The publication date is the day the report or article came out. Cite the first for the price, and mention the second as the place where you found it.
Record the rounding too. The source prints $6.179, which carries three decimal places. If your estimate uses $6.18, write that down next to the source value. A reviewer who checks the source will see a small difference and may assume you made an error if you do not explain it.
Figure 2: $3.665 a year earlier
The same coverage gives a baseline: on the 13th, 2025, the national average was $3.665 a gallon. Cite that figure as the article's number, and check the original page for the agency behind it. Fill in the month from the source before you cite it.
A baseline is a reference point, not a current price. If your bid says diesel is "up sharply from last year," the reader needs to know which year-earlier value you compared against. Without that base date, the claim cannot be checked, and owners tend to challenge unchecked claims.
A 2025 figure is fixed, which makes it the easiest number to stamp. It is also easy to misuse. People often set a year-old baseline next to a price from a different week and produce a percentage that describes nothing real. The safe habit is to compare two figures from the same series, with both dates in the stamp.
Keep the baseline as its own entry in your file rather than a footnote under the current price. Give it its own line in the estimate too. When a bid compares this year to last year, the reader should see the two values side by side, each with its date. A comparison that appears only in narrative text forces the reader to trust your arithmetic. A small table with dates lets them check it in seconds.
Figure 3: a 70.7% rise to $6.18
The Department of Energy reported, as Transport Topics relayed it, that national diesel prices have surged 70.7% from the prior year to $6.18 a gallon. The Transport Topics article on diesel costs carries that line. A large percentage gets attention in a bid narrative, which is why this figure is easy to misuse, and also easy to stamp wrong.
Check the arithmetic before you use it. The 70.7% comparison and the $3.665 baseline come from different reports, and each may use its own dates or series. They may not reconcile. Do not pick one silently. If you quote the 70.7% figure, label it as the Department of Energy's year-over-year comparison, and do not pair it with the baseline in the same sentence.
If you need a percentage for your own estimate, calculate it from two values you have stamped on the same basis, and state which dates you used. If you cannot establish that, leave the percentage out and state the current price with its date.
The $6.18 is the Department of Energy's figure, and the $6.179 is the EIA reading for the 12th. They come from different publishers, so record both and do not treat them as one value. State which figure you used and why, and keep the more precise source value in the file so the rounding can be checked.
Last, note the lag. The Department of Energy's report and the trade article that relays it are different documents, and neither is necessarily the day the price was set. If you use the article's date as the measurement date, you will stamp the figure with the wrong day. Go back to the underlying report where you can, and use the date it gives.
What the three figures tell you together
The three figures agree on direction, but they do not describe a single comparison. The national average reading for the 12th (month and year to be confirmed from the source), as reported through Transport Topics, is $6.179 a gallon. The year-earlier average was $3.665 a gallon. The Department of Energy's year-over-year figure is 70.7%, to $6.18 a gallon. Each one is a true report of a published number, but they do not all share a basis.
Each row carries its own date and purpose. The reading for the 12th and the baseline can be compared once the baseline's publisher is confirmed on the original page. The percentage comes from a different report, with a base that does not line up exactly with the table. Using it as narrative context is fine. Using it as bid math is not, unless you have stamped its base date and confirmed it matches your comparison.
For a bid, the practical rule is simple. Choose one source for the current price and one source for any baseline, and say so. Do not blend a percentage from one report with a dollar figure from another. If the reader asks how you got from one number to the next, the stamp should answer the question without a phone call. For how these figures feed an equipment line, see equipment fuel cost figures.
Where the tax share fits
Transport Topics, citing the Energy Information Administration, reports that taxes account for 11% of the price of diesel at the pump. You can see the same point in the Transport Topics article on dyed diesel relief, where the coverage also notes that diesel prices remain more than 70% above year-ago levels. The tax share is a snapshot for the period the source covers, so stamp it the same way as the price.
Write the phrase "share of pump price" so no one reads 11% as a dollar amount of tax on each gallon. Do not calculate a dollar tax figure unless you have the price for the same date and know which tax applies. The same article covers state-by-state dyed diesel rules. Those rules vary by state, so check each state's rules against its official source before you price tax treatment into a bid.
The tax share also works as a sanity check. If a bid assumes a tax change will move the pump price by a large amount, the 11% share is a reason to ask where that assumption came from. A reviewer who knows that taxes are a small slice of the pump price will want to see the basis for the assumption.
How to write the date stamp
A complete stamp has seven parts. Each one answers a question someone will eventually ask.
- Value and unit: the number as the source printed it, with its unit, such as dollars for each gallon.
- Series: the name the publisher uses for the figure, such as the national average.
- Measurement date: the day the publisher says the price applies.
- Publication date: the day the report or article came out.
- Source and link: the original publisher first, then any article that relayed it.
- Retrieval date: the day you looked at the source for this bid.
- Used in the bid: the value you actually entered, and any rounding you applied.
Diesel, national average, $6.179 a gallon
Measured: [month] 12, [year] (confirm from source)
Published: EIA data, relayed by Transport Topics
Source: https://www.ttnews.com/articles/diesel-spike-fleet-cost-mce
Retrieved: [date you checked the source]
Used in bid: $6.18 a gallon (rounded to the cent)
The retrieval date deserves attention. A link alone is not a stable record. Articles get corrected and updated, and a page you read in one week may show a different figure the next. The retrieval date tells a reviewer what you saw on the day you priced the work. If the page changes later, your stamp still points to what you used.
Put the stamp next to the number in the estimate, not in a separate notes file. Reviewers read the estimate, not your working folder. A stamp that lives only in your notes cannot help the person who has to defend the number. A short line in the estimate keeps the date attached to the figure wherever the figure goes.
Use the same format every time. Consistency makes stamps easy to scan. When every diesel figure in a bid has the same seven parts in the same order, a reviewer can check every figure in a few minutes.
Units and conversions
Many bids mix units. The price may be quoted by the gallon in one document and by the liter in an owner's schedule. Each conversion adds a place where a date can go wrong, because conversion factors are not fixed forever.
The Energy Information Administration's guide to units and calculators says that current conversion factors are updated annually in Appendix A of the Monthly Energy Review. The EIA units and calculators page is the place to start if you need to confirm a factor. A conversion factor belongs to a year, just like a price does, so a factor copied from an old spreadsheet may not match the one EIA currently publishes.
When you convert a number, record three things with it: the factor, the source of the factor, and the year it applies to. Write them in the same stamp as the price. If the conversion is part of the bid math, a reviewer should be able to reproduce your result from the stamp alone.
Avoid converting from memory. A rounded factor can shift a total enough to matter in a large fuel line. Use the factor from the source, carry enough decimal places to match it, and round only at the end, when you present the bid figure.
Common mistakes to avoid
Three mistakes show up most often. The first is copying a figure from an earlier estimate without checking its date. A number that was right for an old bid may be stale for a new one, and nothing in the figure itself says so. The second is treating a trade article as the primary source. Articles are useful for finding a figure, but the stamp should point back to the publisher that produced it. The third is pairing a percentage with a dollar amount from a different date, which produces a comparison no source actually made.
A quieter fourth mistake is rounding before recording. Once the rounded number replaces the source value in your file, nobody can check the rounding later. Keep both values, and the rounding stays visible.
Keeping a record over time
Diesel figures are useful for the bid in front of you and for the next one. Keep a running log with one row for each figure, using the same seven parts as the stamp. When you price a new bid, check the log first, then confirm each value against the source instead of reusing it. Old rows stay in the log with their dates, so you can show how a number was chosen. For a wider check of inputs, see the construction estimate audit.
Review the log after each bid is awarded or lost, and note any figure you would have stamped differently. Over several bids, the log becomes a record of how your estimates were built, which is the record a reviewer will eventually ask for.
A checklist before a diesel figure goes into a bid
Run through these questions for every diesel number before it leaves your desk. None of them takes long, and each one catches a problem that would otherwise show up later.
- Does the stamp include a full date with the month and year, or only a day?
- Is the measurement date separate from the publication date?
- Did you name the original publisher, and not only the article that repeated the number?
- Is the value the one the source printed, with your rounding recorded beside it?
- Does every percentage have a base date that matches the comparison you are making?
- Is the baseline a fixed earlier value from the same series as the current price?
- Does the stamp show the day you retrieved the source for this bid?
- Is the stamp next to the number in the estimate, where a reviewer will see it?
If you cannot answer yes to a question, fix the stamp before you submit. If you cannot find the missing piece, say so in the estimate. An honest note such as "month to be confirmed from source" is far better than a number that looks precise and cannot be checked. Owners generally respect a clearly marked gap more than a confident figure that falls apart when someone asks for its source.
Closing
A date stamp takes seconds to write and can save a difficult conversation later. The three figures in this post show why. A current price, a year-earlier baseline, and a percentage change can each be accurate and still fail to describe the same comparison. The fix is not to avoid diesel figures. The fix is to record where each one came from, when it was measured, and when you looked at it. Do that, and the number in your bid will hold up when someone asks where it came from.