Internal combustion engines and gensets: Correlation
Prices it moves with, and why
Engine prices follow cast iron, steel and aluminium blocks, emission control parts and labour, and demand from vehicles, gensets and machinery. As a producer price index it rises steadily with US manufacturing costs and rarely falls, so it moves slowly.
Price index US PPI: internal combustion engines index · monthly, Jan 2006 to Sep 2026What its price moves with
Selected linkInternal combustion engines and gensets and Steel
Monthly changes -0.00 little or none correlation 12-month changes -0.11 little or none correlation Last 5 years 0.02 monthly changes Lead or lag none No clear lead or lag Price function, Jan 2006 to Sep 2026 Internal combustion engines and gensets ≈ 40.8 × (Steel)0.27 R² 0.55 On this fit, a 10% higher steel price goes with a 2.6% higher internal combustion engines and gensets price over the long run. Units: index and index, BLS base period.Chart: Internal combustion engines and gensets and Steel prices rebased to 100 at Jan 2006, log scale
Both prices rebased to 100 at Jan 2006, on a log scale so equal percentage moves look the same size.Chart: Internal combustion engines and gensets price against Steel price, monthly, log scales, with fitted line
Each dot is one month; paler dots are older (2006), darker dots recent (2026); the ringed dot is the latest month. The dashed line is the fitted price function. Both axes are logarithmic.Blocks, crankshafts and many parts are iron and steel. Even so, monthly moves hardly correlate with the steel index, and yearly moves correlate at -0.11, because engine makers set prices on annual contracts and absorb or hedge metal swings.
little or none co-movement month to month · 249 months Show chartsCylinder heads and many car engine blocks are cast aluminium to save weight. The link is faint in the data, with monthly moves over the last five years correlating at 0.16, since metal is a modest share of a finished engine and makers reprice only occasionally.
little or none co-movement month to month · 249 months Show chartsEngines burn petrol and diesel made from crude oil, so very high fuel prices can push buyers toward smaller or electric options. The index barely reacts, with monthly moves correlating at 0.10, because engine demand changes slowly with vehicle and equipment fleets.
little or none co-movement month to month · 249 months Show chartsDiesel and gas gensets pair an engine with a generator, and both are made by similar machinery firms. Monthly moves correlate at 0.30, and yearly moves more strongly, reflecting shared US manufacturing costs and the same industrial demand cycle.
weak co-movement month to month · 249 months Show chartsGearboxes, couplings and drives are bought alongside engines for vehicles and machinery. Monthly moves correlate at 0.34 and yearly moves at 0.79, a common driver: both are US machinery prices that follow labour, steel and capital spending.
weak co-movement month to month · 249 months Show chartsCatalytic converters using platinum-group metals are required on most engines, adding cost when metal prices rise. The platinum proxy shows little link, correlating at 0.13 monthly, because catalyst costs are passed on only with model or contract changes.
little or none co-movement month to month · 249 months Show chartsHow to read these numbers
Correlation of monthly changes (the number in the coloured pill) compares how much each price moved, month by month, since 2006 or the first month both series exist. It runs from −1 to +1: near +1 the two usually rise and fall in the same months, near 0 there is no link, and a negative number means they tend to move in opposite directions. Above 0.7 is strong, 0.4 to 0.7 moderate, 0.2 to 0.4 weak.
12-month changes compare year-on-year moves, which shows whether two prices share the same cycles even when the month-to-month noise differs.
Price function is a straight-line fit of the two prices on logarithmic scales: price ≈ k × (partner price)β. β is how much this price moves, in per cent, for a 1% move in the partner over the whole period, and R² is the share of the variation the fit explains. Two prices that both drift up with inflation can fit well without any real link, so read it together with the monthly correlation.
Lead or lag checks whether the monthly correlation is clearly higher when one price is shifted by 1 to 6 months.
Correlation is not cause. The reasons on each card explain the economic link; the numbers show how strongly it has shown up in prices. Proxy series are US producer price indexes or related prices and can blur the real link.
Data: World Bank Commodity Price Data (Pink Sheet), October 2026; US Bureau of Labor Statistics producer price indexes, IMF primary commodity prices and US EIA prices via FRED, Federal Reserve Bank of St. Louis, retrieved November 2026. Calculations by this site.